Refrigeration cycle apparatus

ABSTRACT

A refrigeration cycle apparatus including a heat source side heat exchanger including a first heat exchanger and a second heat exchanger connected in parallel; an air-sending device that supplies air, which is an object to be heat exchanged in the first heat exchanger and the second heat exchanger, in a variable manner; solenoid valves that each opens and closes a refrigerant passage of the first heat exchanger and the second heat exchanger; a third refrigerant circuit that is parallelly connected to the first heat exchanger and the second heat exchanger; and a flow control valve that controls the flow rate of the refrigerant flowing in the third refrigerant circuit. The refrigeration cycle apparatus can improve continuity of control of a heat exchange capacity of a heat source side heat exchanger.

TECHNICAL FIELD

The present invention relates to a refrigeration cycle apparatus, inparticular, a refrigeration cycle apparatus capable of continuouslycontrolling a heat exchange capacity of a heat source side heatexchanger.

BACKGROUND ART

To enable continuous control of a heat exchange capacity of a heatsource side heat exchanger, a conventional refrigeration cycle apparatusis proposed in, for example, Patent Literature 1 such that “a heatsource unit side heat exchanger is formed by connecting a firstrefrigerant circuit 21, a second refrigerant circuit 22, and a thirdrefrigerant circuit 23 that has been branched and that has beenconnected in parallel to each other. A first heat exchanger 24 isdisposed in the first refrigerant circuit 21; a first solenoid valve 3 afor opening/closing the heat source unit side heat exchanger is providedin one end of the first heat exchanger 24 on the four-way valve 2 side,which is capable of opening/closing a two way flow; and a third solenoidvalve 3 c for opening/closing the heat source unit side heat exchangeris provided in the other end of the first heat exchanger 24, which iscapable of opening/closing a two way flow. Distribution of a refrigerantto the first refrigerant circuit 21 is controlled with theopening/closing of the two solenoid valves 3 a and 3 c, and whether heatexchange is carried out in the first heat exchanger 24 is controlled. Asecond heat exchanger 25 is disposed in the second refrigerant circuit22; a second solenoid valve 3 b for opening/closing the heat source unitside heat exchanger is provided in one end of the second heat exchanger25 on the four-way valve 2 side, which is capable of opening/closing atwo way flow; and a fourth solenoid valve 3 d for opening/closing theheat source unit side heat exchanger is provided in the other end of thesecond heat exchanger 25, which is capable of opening/closing a two wayflow. Distribution of the refrigerant to the first refrigerant circuit22 is controlled with the opening/closing of the two solenoid valves 3 band 3 d, and whether heat exchange is carried out in the second heatexchanger 25 is controlled. A solenoid valve 3 e for bypassing the firstheat source unit side heat exchanger, which is capable ofopening/closing a two way flow, is disposed mid-way of the piping of thethird refrigerant circuit 23, and whether there will be a refrigerantflow bypassing the first heat exchanger 24 and the second heat exchanger25 is controlled with the opening/closing of the solenoid valve 3 e.

. . . The capacity of the heat source unit side heat exchanger iscontrolled by the following four stages. . . . A first stage correspondsto a case in which the required capacity of the heat source unit sideheat exchanger is the largest, . . . refrigerant is made to flow intoboth the first and second heat exchangers 24 and 25 and no refrigerantis made to flow into the third refrigerant circuit 23 while an airvolume of a heat source unit side air-sending device 18 is controlled bycontrolling the air-sending device from stop to full speed with aninverter or the like (not shown). . . . A second stage corresponds to acase in which the required capacity of the heat source unit side heatexchanger is second largest next to the first stage, . . . refrigerantis made to flow into only the second heat exchanger 25 and . . . norefrigerant is made to flow into the first heat exchanger 24 and thethird refrigerant circuit 23 to substantially reduce the heat transferarea of the heat source unit side heat exchanger 3 while an air volumeof a heat source unit side air-sending device 18 is controlled bycontrolling the air-sending device from stop to full speed with aninverter or the like (not shown). . . . A third stage corresponds to acase in which the required capacity of the heat source unit side heatexchanger is smaller than that of the second stage, . . . refrigerant ismade to flow into the second heat exchanger 25 and the third refrigerantcircuit 23 and no refrigerant is made to flow into the first refrigerantcircuit 21, that is, the first heat exchanger 24 to substantially reducethe heat transfer area of the heat source unit side heat exchanger 3 andreduce the flow rate of the refrigerant to the second heat exchanger 25while an air volume of a heat source unit side air-sending device 18 iscontrolled by controlling the air-sending device from stop to full speedwith an inverter or the like (not shown). . . . A fourth stepcorresponds to a case in which the required capacity of the heat sourceunit side heat exchanger is the smallest in which the solenoid valve 3 efor bypassing the first heat source unit side heat exchanger is openedand the first, second, third, and fourth solenoid valves 3 a, 3 b, 3 c,and 3 d are closed so that there will be no heat exchange in the heatsource unit side heat exchanger 3.

. . . Even if there is outside wind, the first stage and the secondstage can be continuously controlled on condition that the capacity AK2_(MAX) of the heat source unit side heat exchanger when the heat sourceunit side air-sending device 18 in the second stage is run at full speedis larger than the capacity AK1 _(MAX) of the heat source unit side heatexchanger when the heat source unit side air-sending device 18 isstopped, that is, when the wind velocity of the outside wind allows AK2_(MAX)>AK1 _(MAX). Similarly, even if there is outside wind, the secondstage and the third stage can be continuously controlled on conditionthat the capacity AK3 _(MAX) of the heat source unit side heat exchangerwhen the heat source unit side air-sending device 18 in the third stageis run at full speed is equivalent to the outside wind of the secondstage and is larger than the capacity AK2 _(MAX) of the heat source unitside heat exchanger when the heat source unit side air-sending device 18is stopped, that is, when AK3 _(MAX)>AK3 _(MAX).

CITATION LIST Patent Literature

-   Patent Literature 1: Japanese Patent No. 4211094 (paragraphs 0003,    0017, and 0018 and FIGS. 26 and 30)

SUMMARY OF INVENTION Technical Problem

Incidentally, in the above conventional refrigeration cycle apparatuses,the following problems have been encountered.

First, in a supply device that supplies an object to be heat exchangedto the heat source side heat exchanger, there are cases in which thesupply amount of the object to be heat exchanged to the heat source sideheat exchanger cannot be continuously controlled from its maximum supplyamount to zero. For example, there is an air-sending device in which itsminimum rotation speed (minimum air volume) is specified so that themotor driving the air-sending device is cooled. In such an air-sendingdevice, the control of air volume cannot be carried out continuouslyfrom full speed to stop. Accordingly, in each stage where the number ofheat exchangers in which refrigerant flows in is gradually increased ordecreased, there is a case in which (the minimum heat exchange capacityof the heat source side heat exchanger that is in a stage with a largerheat exchange capacity) becomes larger than (the maximum heat exchangecapacity of the heat source side heat exchanger that is in a stage witha smaller heat exchange capacity). Thus, a problem has been encounteredin that during shifting of each stage where the number of heatexchangers in which refrigerant flows in is gradually increased ordecreased, the heat exchange capacity of the heat source side heatexchanger cannot be continuously controlled.

Further, when continuously controlling the heat exchange capacity of aheat source side heat exchanger with a supply device that cannotcontinuously control the supply amount of the object to be heatexchanged to the heat source side heat exchanger from maximum supplyamount to zero, the number of heat exchangers constituting the heatsource side heat exchanger needs to be increased so as to reduce thedifference of the heat exchange capacity of each stage where the numberof heat exchangers in which refrigerant flows in is gradually increasedor decreased. Accordingly, the number of solenoid valves and the likethat open/close the refrigerant passage to each heat exchangerdisadvantageously increased.

The present invention has been made to overcome the above knownproblems, and an object thereof is to provide a refrigeration cycleapparatus that is capable of continuously controlling the heat exchangecapacity of a heat source side heat exchanger without increasing thenumber of heat exchangers that constitute the heat source side heatexchanger even when the supply amount of the object to be heat exchangedto the heat source side heat exchanger cannot be continuously controlledfrom its maximum supply amount to zero.

Solution to Problem

A refrigeration cycle apparatus according to the invention includes aheat source side heat exchanger having a plurality of heat exchangersconnected in parallel; a supply device supplying, in a variable manner,an object to be heat exchanged that exchanges heat with a refrigerantthat flows in the heat exchangers to the heat exchangers;

passage on-off devices opening and closing refrigerant passages of theheat exchangers, respectively; a bypass piping being connected to theheat exchangers in parallel; and a flow control device being provided inthe bypass piping, the flow control device controlling a flow rate ofthe refrigerant flowing in the bypass piping.

Advantageous Effects of Invention

In the invention, during shifting of each stage where a number of heatexchangers in which refrigerant flows in is gradually increased ordecreased, a heat exchange capacity of a heat source side heat exchangercan be continuously controlled by distributing the refrigerant in abypass piping and by continuously increasing or decreasing the flow rateof the refrigerant that is flowing in the bypass piping with a flowcontrol device.

Accordingly, it will be possible to make (a minimum heat exchangecapacity of a heat source side heat exchanger that is in a stage with alarger heat exchange capacity) to become smaller than (a maximum heatexchange capacity of a heat source side heat exchanger that is in astage with a smaller heat exchange capacity) even with a supply devicethat cannot continuously control a supply amount of an object to be heatexchanged to the heat source side heat exchanger from maximum supplyamount to zero.

Thus even in a case in which the supply amount of the object to be heatexchanged to the heat source side heat exchanger cannot be continuouslycontrolled from its maximum supply amount to zero, it will be capable tocontinuously control the heat exchange capacity of the heat source sideheat exchanger without increasing the number of heat exchangers thatconstitute the heat source side heat exchanger.

Note the distribution of the refrigerant to the bypass piping does nothave to be performed in all of the stages where the number of heatexchangers in which the refrigerant flows in is gradually increased ordecreased but can be performed at desired stages.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram illustrating a refrigerant circuit of anair-conditioning apparatus as an example of a refrigeration cycleapparatus of Embodiment 1 of the invention.

FIG. 2 is a diagram illustrating flows of a refrigerant in a refrigerantcircuit of an air-conditioning apparatus during a cooling operation anda heating operation as an example of a refrigeration cycle apparatus ofEmbodiment 1 of the invention.

FIG. 3 is a diagram illustrating flows of a refrigerant in a refrigerantcircuit of an air-conditioning apparatus during a heating main operationas an example of a refrigeration cycle apparatus of Embodiment 1 of theinvention.

FIG. 4 is a diagram illustrating flows of a refrigerant in a refrigerantcircuit of an air-conditioning apparatus during a cooling main operationas an example of a refrigeration cycle apparatus of Embodiment 1 of theinvention.

FIG. 5 is a diagram illustrating a control content of a heat exchangecapacity regulating device of an air-conditioning apparatus as anexample of a refrigeration cycle apparatus of Embodiment 1 of theinvention.

FIG. 6 is a diagram illustrating a control flow of a heat exchangecapacity regulating device when the heat source side heat exchanger ofan air-conditioning apparatus is functioning as a condenser as anexample of a refrigeration cycle apparatus of Embodiment 1 of theinvention.

FIG. 7 is a diagram illustrating a control flow of a heat exchangecapacity regulating device when the heat source side heat exchanger ofan air-conditioning apparatus is functioning as an evaporator as anexample of a refrigeration cycle apparatus of Embodiment 1 of theinvention.

FIG. 8 is a diagram illustrating a refrigerant circuit of anair-conditioning apparatus as another example of a refrigeration cycleapparatus of Embodiment 1 of the invention.

FIG. 9 is a diagram illustrating a refrigerant circuit of anair-conditioning apparatus as an example of a refrigeration cycleapparatus of Embodiment 2 of the invention.

FIG. 10 is a diagram illustrating a flow of a refrigerant in arefrigerant circuit of an air-conditioning apparatus during a coolingonly operation as an example of a refrigeration cycle apparatus ofEmbodiment 2 of the invention.

FIG. 11 is a diagram illustrating a control flow of a heat exchangecapacity regulating device when the heat source side heat exchanger ofan air-conditioning apparatus is functioning as a condenser as anexample of a refrigeration cycle apparatus of Embodiment 2 of theinvention.

FIG. 12 is a diagram illustrating a refrigerant circuit of anair-conditioning apparatus as an example of a refrigeration cycleapparatus of Embodiment 3 of the invention.

FIG. 13 is a diagram illustrating flows of a refrigerant in arefrigerant circuit of an air-conditioning apparatus during a coolingoperation and a heating operation as an example of a refrigeration cycleapparatus of Embodiment 3 of the invention.

FIG. 14 is a diagram illustrating flows of a refrigerant in arefrigerant circuit of an air-conditioning apparatus during a heatingmain operation as an example of a refrigeration cycle apparatus ofEmbodiment 3 of the invention.

FIG. 15 is a diagram illustrating flows of a refrigerant in arefrigerant circuit of an air-conditioning apparatus during a coolingmain operation as an example of a refrigeration cycle apparatus ofEmbodiment 3 of the invention.

DESCRIPTION OF EMBODIMENTS

Subsequently, embodiments of the present invention will be describedbelow with reference to the drawings.

Embodiment 1

FIG. 1 is a diagram illustrating a refrigerant circuit of anair-conditioning apparatus as an example of a refrigeration cycleapparatus of Embodiment 1 of the invention.

The air-conditioning apparatus according to Embodiment 1 is an exemplarymulti-room heat pump air conditioning system in which a plurality ofindoor units is connected to a single heat source unit and in whichcooling can be selected in one or some indoor units while heating can beselected in one or some of the remaining indoor units. Thisair-conditioning apparatus includes a heat source unit A, a relay unitE, and a parallelly connected indoor units B, C, and D.

(Heat Source Unit A)

The heat source unit A includes a compressor 1, a four-way valve 2, aheat source side heat exchanger 3, an air-sending device 18, which iscapable of variably controlling the volume of air and which sends air tothe heat source side heat exchanger 3, and a switching valve 4 thatswitches a passage of a refrigerant discharged from the compressor 1.

The air-sending device 18 corresponds to the supply device of theinvention. Note that in Embodiment 1, the object to be heat exchanged,which exchanges heat with the refrigerant flowing in the heat sourceside heat exchanger 3, is air. For example, when the object to be heatexchanged, which exchanges heat with the refrigerant flowing in the heatsource side heat exchanger 3, is water or brine, a pump or the like maybe used as the supply device that supplies the object to be heatexchanged to the heat source side heat exchanger 3.

The heat source side heat exchanger 3 includes a plurality of heatexchangers connected in parallel. In Embodiment 1, two heat exchangers(a first heat exchanger 24 and a second heat exchanger 25) are connectedin parallel. More specifically, the heat source side heat exchanger 3includes a branched and parallelly connected a first refrigerant circuit21, a second refrigerant circuit 22, and a third refrigerant circuit 23.The first heat exchanger 24 is disposed in the first refrigerant circuit21. At one end of the first heat exchanger 24 on the four-way valve 2side, a solenoid valve 3 a is disposed, and at the other end of thefirst heat exchanger 24, a solenoid valve 3 c is disposed. Theopening/closing of the two solenoid valves 3 a and 3 c (opening/closingof the refrigerant passage) controls the distribution of the refrigerantto the first refrigerant circuit 21 and whether heat exchange is carriedout in the first heat exchanger 24. The second heat exchanger 25 isdisposed in the second refrigerant circuit 22. At one end of the secondheat exchanger 25 on the four-way valve 2 side, a solenoid valve 3 b isdisposed, and at the other end of the first heat exchanger 25, asolenoid valve 3 d is disposed. The opening/closing of the two solenoidvalves 3 b and 3 d (opening/closing of the refrigerant passage) controlsthe distribution of the refrigerant to the second refrigerant circuit 22and whether heat exchange is carried out in the second heat exchanger25. A flow control valve 40 is disposed mid-way of the piping of thethird refrigerant circuit 23. The flow control valve 40 controls theflow rate of the refrigerant that bypasses the first heat exchanger 24and the second heat exchanger 25 (the flow rate of the refrigerant thatflows through the third refrigerant circuit 23).

The solenoid valves 3 a to 3 d correspond to the passage on-off devicesof the invention. The third refrigerant circuit 23 corresponds to thebypass piping of the invention. The flow control valve 40 corresponds tothe flow control device of the invention. Note that although inEmbodiment 1, devices with a valve structure is employed as the passageon-off devices and the flow control device, Embodiment 1 is not limitedto these devices. The structure of the passage on-off device may be anythat can open and close the refrigerant passage of the first heatexchanger 24 and the second heat exchanger 25. Further, the structure ofthe flow control device may be any that can control the flow rate of therefrigerant flowing in the third refrigerant circuit 23.

The switching valve 4 includes four check valves (first check valve 4 a,second check valve 4 b, third check valve 4 c, and fourth check valve 4d).

The fourth check valve 4 d is provided between the heat source side heatexchanger 3 and a second heat source unit side connecting piping 16A,and permits the refrigerant to flow only from the heat source side heatexchanger 3 to the second heat source unit side connecting piping 16A.The first check valve 4 a is provided between the four-way valve 2 ofthe heat source unit A and a first heat source unit side connectingpiping 15A, and permits the refrigerant to flow only from the first heatsource unit side connecting piping 15A to the four-way valve 2. Thethird check valve 4 c is provided between the four-way valve 2 of theheat source unit A and a second heat source unit side connecting piping16A, and permits the refrigerant to flow only from the four-way valve 2to the second heat source unit side connecting piping 16A. The secondcheck valve 4 b is a second check valve that is provided between theheat source side heat exchanger 3 and the first heat source unit sideconnecting piping 15A, and permits the refrigerant to flow only from thefirst heat source unit side connecting piping 15A to the heat sourceside heat exchanger 3.

The other end of the second heat source unit side connecting piping 16Ais connected to a gas-liquid separator 7 of the relay unit E to bedescribed below. The other end of the first heat source unit sideconnecting piping 15A is connected to a first branching unit 5 of therelay unit E to be described below.

By providing the switching valve 4, the refrigerant that has beendischarged from the compressor 1 always passes through the second heatsource unit side connecting piping 16A and flows into the relay unit E,and refrigerant flowing out of the relay unit E always passes throughthe first heat source unit side connecting piping 15A. Accordingly, thepipe diameter of the second heat source unit side connecting piping 16Acan be narrower than the pipe diameter of the first heat source unitside connecting piping 15A.

Further, a condensing temperature detection device 19 and an evaporatingtemperature detection device 20 that are temperature sensors and thelike are provided to the heat source unit A, for example. The condensingtemperature detection device 19 is provided in the high-pressure portionof the refrigeration cycle and, in Embodiment 1, is provided in thedischarge piping of the compressor 1. The evaporating temperaturedetection device 20 is provided in the low-pressure portion of therefrigeration cycle and, in Embodiment 1, is provided in the suctionpiping of the compressor 1.

(Indoor Units B, C, and D)

The indoor units B, C, and D each have the same configuration.

In more detail, the indoor unit B includes an indoor unit side heatexchanger 10B. One end of the indoor unit side heat exchanger 10B isconnected to the first branching unit 5 of the relay unit E to bedescribed below via a first indoor unit side connecting piping 15B. Theother end of the indoor unit side heat exchanger 10B is connected to asecond branching unit 6 of the relay unit E to be described below via asecond indoor unit side connecting piping 16B. A flow control valve 11Bis provided to the second indoor unit side connecting piping 16B.

The indoor unit C includes an indoor unit side heat exchanger 10C. Oneend of the indoor unit side heat exchanger 10C is connected to the firstbranching unit 5 of the relay unit E to be described below via a firstindoor unit side connecting piping 15C. The other end of the indoor unitside heat exchanger 10C is connected to the second branching unit 6 ofthe relay unit E to be described below via a second indoor unit sideconnecting piping 16C. A flow control valve 11C is provided to thesecond indoor unit side connecting piping 16C.

The indoor unit D includes an indoor unit side heat exchanger 10D. Oneend of the indoor unit side heat exchanger 10D is connected to the firstbranching unit 5 of the relay unit E to be described below via a firstindoor unit side connecting piping 15D. The other end of the indoor unitside heat exchanger 10D is connected to the second branching unit 6 ofthe relay unit E to be described below via a second indoor unit sideconnecting piping 16D. A flow control valve 11D is provided to thesecond indoor unit side connecting piping 16D.

(Relay Unit E)

The relay unit E includes the first branching unit 5, the secondbranching unit 6, the gas-liquid separator 7, a flow control valve 8,and a flow control valve 9.

The first branching unit 5 includes solenoid valves 13B, 13C, and 13Dand solenoid valves 14B, 14C, and 14D.

One end of each of the solenoid valves 13B, 13C, and 13D is connected tothe first heat source unit side connecting piping 15A. Further, theother end of the solenoid valve 13B is connected to the first indoorunit side connecting piping 15B, the other end of the solenoid valve 13Cis connected to the first indoor unit side connecting piping 15C, andthe other end of the solenoid valve 13D is connected to the first indoorunit side connecting piping 15D.

One end of each of the solenoid valves 14B, 14C, and 14D is connected tothe gas-liquid separator 7. Further, the other end of the solenoid valve14B is connected to the first indoor unit side connecting piping 15B,the other end of the solenoid valve 14C is connected to the first indoorunit side connecting piping 15C, and the other end of the solenoid valve14D is connected to the first indoor unit side connecting piping 15D.

The second branching unit 6 branchingly connects the second indoor unitside connecting piping 16 b, 16 c, and 16 d to the second heat sourceunit side connecting piping 16A. The gas-liquid separator 7 is providedin the second heat source unit side connecting piping 16A and its gasphase portion is connected to the solenoid valves 14 b, 14 c, and 14 d,and its liquid phase portion is connected to the second branching unit6. The flow control valve 8 is connected between the gas-liquidseparator 7 and the second branching unit 6 and the flow control valve 9is connected between the second branching unit 6 and the first heatsource unit side connecting piping 15A. In Embodiment 1, an electronicexpansion valve is employed to each of the flow control valves 8 and 9.

<Flow of Refrigerant>

The flow of the refrigerant of the air-conditioning apparatus accordingto Embodiment 1 will be described with reference to FIGS. 2, 3, and 4.In FIG. 2, flows of the refrigerant will be described in a case whereonly cooling is operated (hereinafter, referred to as a “cooling onlyoperation”) and in a case where only heating is operated (hereinafter,referred to as a “heating only operation”). In FIG. 3, a flow of therefrigerant will be described in a case where cooling and heatingco-exists and the heat source side heat exchanger 3 functions as acondenser (hereinafter, referred to as a “cooling main operation”). InFIG. 4, a flow of the refrigerant will be described in a case wherecooling and heating co-exists and the heat source side heat exchanger 3functions as an evaporator (hereinafter, referred to as a “heating mainoperation”).

(Flow of Refrigerant During Cooling Only Operation)

FIG. 2 is a diagram illustrating flows of the refrigerant in therefrigerant circuit of the air-conditioning apparatus during the coolingoperation and the heating operation as an example of the refrigerationcycle apparatus of Embodiment 1 of the invention. The direction of thesolid arrows in FIG. 2 indicates the direction of the refrigerant flowduring the cooling only operation.

A high-temperature high-pressure gas refrigerant that has beendischarged from the compressor 1 flows into the four-way valve 2. Therefrigerant that has flowed out of the four-way valve 2 flows into theheat source side heat exchanger 3. The refrigerant that has flowed intothe heat source side heat exchanger 3 exchanges heat with the air sentby the air-sending device 18 and is condensed and liquefied. Thecondensed and liquefied, high-pressure liquid refrigerant flows throughthe fourth check valve 4 d, passes through the second heat source unitside connecting piping 16A, gas-liquid separator 7, and the flow controlvalve 8 in this order, and flows into the second branching unit 6. Thehigh-pressure liquid refrigerant that has flowed into the secondbranching unit 6 passes through the second indoor unit side connectingpipings 16 b, 16 c, and 16 d and flows into each of the respectiveindoor units B, C, and D. Further, the refrigerant that has flowed intoeach of the indoor units B, C, and D is decompressed to low pressure inthe corresponding flow control valves 11B, 11C, and 11D, exchanges heatin the indoor unit side heat exchangers 10B, 10C, and 10D with theindoor air, and is evaporated and gasified to cool the indoor space.Note that the opening degree of each of the flow control valves 11B,11C, and 11D is controlled on the basis of the amount of superheat atthe outlet of the indoor unit side heat exchangers 10B, 10C, and 10D,respectively. Then, this refrigerant that has turned into a gaseousstate passes through the first indoor unit side connecting pipings 15B,15C, and 15D, the solenoid valves 13B, 13C, and 13D, the first branchingunit 5, the first heat source unit side connecting piping 15A, the firstcheck valve 4 a, and the four-way valve 2, and is sucked into thecompressor 1.

During the cooling only operation, the solenoid valves 13B, 13C, and 13Dare opened, the solenoid valves 14B, 14C, and 14D are closed. As such,the refrigerant flows in the solid arrow direction in the first indoorunit side connecting pipings 15B, 15C, and 15D, the second indoor unitside connecting pipings 16B, 16C, and 16D, and the indoor units B, C,and D. Further, since the first heat source unit side connecting piping15A is low in pressure, the second heat source unit side connectingpiping 16A is high in pressure, the end connection of the heat sourceside heat exchanger 3 to the switching valve 4 is high in pressure, andthe end connection of the four-way valve 2 to the switching valve 4 islow in pressure, the refrigerant inevitably flows to the first checkvalve 4 a and the fourth check valve 4 d.

(Flow of Refrigerant During Heating Only Operation)

The direction of the broken-line arrows in FIG. 2 indicates thedirection of the refrigerant flow during the heating only operation.

A high-temperature high-pressure gas refrigerant that has beendischarged from the compressor 1 flows into the four-way valve 2. Therefrigerant that has flowed out of the four-way valve 2, passes throughthe third check valve 4 c, the second heat source unit side connectingpiping 16A, and the gas-liquid separator 7 and flows into the firstbranching unit 5. The high-temperature high-pressure gas refrigerantthat has flowed into the first branching unit 5 passes through each ofthe solenoid valves 14B, 14C, and 14D and the corresponding first indoorunit side connecting pipings 15 b, 15 c, and 15 d in this order andflows into each of the respective indoor units B, C, and D. Then thehigh-temperature high-pressure gas refrigerant that has flowed into eachof the indoor units B, C, and D exchanges heat in the respective indoorunit side heat exchangers 10B, 10C, and 10D and is condensed andliquefied to heat the indoor space.

This refrigerant that has turned into a liquid state passes through theflow control valves 11B, 11C, and 11D whose opening degree, which hasbeen controlled on the basis of the amount of subcooling at the outletof each of the indoor unit side heat exchangers 10B, 10C, and 10D, arein a nearly fully opened state, flows into the second branching unit 6through the second indoor unit side connecting pipings 16B, 16C, and 16Dand is merged, and further passes through the third flow control valve9. Here, the liquid refrigerant that has left the indoor unit side heatexchangers 10B, 10C, and 10D is decompressed into a low-pressuretwo-phase gas-liquid state in either the flow control valves 11B, 11C,and 11D or the third flow control valve 9.

This refrigerant in a low-pressure two-phase gas-liquid state flows intothe first heat source unit side connecting piping 15A. The refrigerantin a low-pressure two-phase state that has flowed into the first heatsource unit side connecting piping 15A flows into the heat source sideheat exchanger 3. The refrigerant that has flowed into the heat sourceside heat exchanger 3 exchanges heat with the air sent by theair-sending device 18, which is capable of variably controlling thevolume of air, and is evaporated and gasified. The refrigerant that hasturned into a gaseous state passes through the four-way valve 2 of theheat source unit and is sucked into the compressor 1.

During the heating only operation, the solenoid valves 14B, 14C, and 14Dare opened, the solenoid valves 13B, 13C, and 13D are closed. As such,the refrigerant flows in the broken-line arrow direction in the firstindoor unit side connecting piping 15B, 15C, and 15D, the second indoorunit side connecting piping 16B, 16C, and 16D, and the indoor units B,C, and D. Further, since the first heat source unit side connectingpiping 15A is low in pressure, the second heat source unit sideconnecting piping 16A is high in pressure, the end connection of theheat source side heat exchanger 3 to the switching valve 4 is low inpressure, and the end connection of the four-way valve 2 to theswitching valve 4 is high in pressure, the refrigerant inevitably flowsto the second check valve 4 b and the third check valve 4 c.

(Flow of Refrigerant During Heating Main Operation)

FIG. 3 is a diagram illustrating flows of the refrigerant in therefrigerant circuit of the air-conditioning apparatus during the heatingmain operation as an example of the refrigeration cycle apparatus ofEmbodiment 1 of the invention. The direction of the broken-line arrowsin FIG. 3 indicates the direction of the refrigerant flow during theheating main operation. Note that in FIG. 3, a case in which the indoorunits B and C carry out heating operation and the indoor unit D carriesout cooling operation is illustrated.

A high-temperature high-pressure gas refrigerant that has beendischarged from the compressor 1 flows into the four-way valve 2. Therefrigerant that has flowed out of the four-way valve 2, passes throughthe third check valve 4 c, the second heat source unit side connectingpiping 16A, and the gas-liquid separator 7 and flows into the firstbranching unit 5. The high-temperature high-pressure gas refrigerantthat has flowed into the first branching unit 5 passes through each ofthe solenoid valves 14B and 14C, the corresponding first indoor unitside connecting pipings 15B and 15C in this order, and flows into eachof the respective indoor units B and C. Then the high-temperaturehigh-pressure gas refrigerant that has flowed into each of the indoorunits B and C exchanges heat with the indoor air and is condensed andliquefied to heat the indoor space. This refrigerant that has turnedinto a liquid state passes through the flow control valves 11B and 11Cwhose opening degree, which has been controlled on the basis of theamount of subcooling at the outlet of each of the indoor unit side heatexchangers 10B and 10C, are in a nearly fully opened state, is slightlydecompressed, and flows into the second branching unit 6 through thesecond indoor unit side connecting pipings 16B and 16C.

A portion of the refrigerant that has flowed into the second branchingunit 6 passes through the second indoor unit side connecting piping 16Dand enters the indoor unit D that is about to perform cooling. Thisrefrigerant enters the flow control valve 11D that is controlled by theamount of superheat at the outlet of the indoor unit side heat exchanger10D and is decompressed. The decompressed refrigerant exchanges heat inthe indoor unit side heat exchanger 10D, is evaporated and gasified tocool the indoor space. This refrigerant that has turned into a gaseousstate passes through the solenoid valve 13D and flows into the firstheat source unit side connecting piping 15A.

Meanwhile, the remaining refrigerant in the second branching unit 6passes through the third flow control valve 9 that is controlled suchthat the pressure difference between the high pressure (for example, thepressure of the second heat source unit side connecting piping 16A) andthe middle pressure (for example, the pressures of the second indoorunit side connecting piping 16B, 16C, and 16D) is within a predeterminedrange. Subsequently, this refrigerant merges in the first heat sourceunit side connecting piping 15A with the refrigerant that has passedthrough the indoor unit D that was about to perform cooling.

The low-pressure two-phase refrigerant that has flowed into the firstheat source unit side connecting piping 15A flows into the heat sourceunit A, passes through the second check valve 4 b, and flows into theheat source side heat exchanger 3. Here, the refrigerant that hasevaporated and has turned into a gaseous state after exchanging heatwith the air sent from the air-sending device 18, which is capable ofvariably controlling the volume of air, flows through the four-way valve2 of the heat source unit and is sucked into the compressor 1.

During the heating main operation, since the solenoid valves 14B and 14Care opened, and the solenoid valves 13B and 13C are closed, in the firstindoor unit side connecting pipings 15B and 15C, the second indoor unitside connecting pipings 16B and 16C, and the indoor units B and C therefrigerant flows in the direction of the broken-line arrows, andheating is performed. Further, since the solenoid valve 14D is closedand the solenoid valve 13D is opened, in the first indoor unit sideconnecting piping 15D, the second indoor unit side connecting piping16D, and the indoor unit D, the refrigerant flows in the direction ofthe broken-line arrows, and cooling is performed. Further, since thefirst heat source unit side connecting piping 15A is low in pressure,the second heat source unit side connecting piping 16A is high inpressure, the end connection of the heat source side heat exchanger 3 tothe switching valve 4 is low in pressure, and the end connection of thefour-way valve 2 to the switching valve 4 is high in pressure, therefrigerant inevitably flows to the second check valve 4 b and the thirdcheck valve 4 c.

(Flow of Refrigerant During Cooling Main Operation)

FIG. 4 is a diagram illustrating flows of the refrigerant in therefrigerant circuit of the air-conditioning apparatus during the coolingmain operation as an example of the refrigeration cycle apparatus ofEmbodiment 1 of the invention. The direction of the broken-line arrowsin FIG. 4 indicates the direction of the refrigerant flow during thecooling main operation. Note that in FIG. 4, a case in which the indoorunits B and C carry out cooling operation and the indoor unit D carriesout heating operation is illustrated.

A high-temperature high-pressure gas refrigerant that has beendischarged from the compressor 1 flows into the four-way valve 2. Therefrigerant that has flowed out of the four-way valve 2 flows into theheat source side heat exchanger 3. The refrigerant that has flowed intothe heat source side heat exchanger 3 exchanges heat with the air sentby the air-sending device 18 and is moderately condensed and liquefied,and turns into a high-temperature high-pressure two-phase state. Thishigh-temperature high-pressure two-phase refrigerant passes through thefourth check valve 4 d and flows into the gas-liquid separator 7 of therelay unit E. The refrigerant that has flowed into the gas-liquidseparator 7 is separated into gas refrigerant and liquid refrigerant.

The gas refrigerant that has been separated in the gas-liquid separator7 passes through the first branching unit 5, the solenoid valve 14D, andthe first indoor unit side connecting piping 15D in this order, andflows into the indoor unit D that is about to perform heating. The gasrefrigerant that has flowed into the indoor unit D exchanges heat in theindoor unit side heat exchangers 10D and is condensed and liquefied toheat the indoor space. Further, the liquid refrigerant that has flowedout of the indoor unit side heat exchanger 10D is decompressed in thecourse of passing through the flow control valve 11D whose openingdegree, which has been controlled on the basis of the amount ofsubcooling at the outlet of the indoor unit side heat exchanger 10D, isin a nearly fully opened state, is slightly decompressed, and flows intothe second indoor unit side connecting piping 16D into the secondbranching unit 6.

Meanwhile, the liquid refrigerant that has been separated in thegas-liquid separator 7 passes through the flow control valve 8 that iscontrolled such that the pressure difference between the high pressure(for example, the pressure of the second heat source unit sideconnecting piping 16A) and the middle pressure (for example, thepressures of the second indoor unit side connecting piping 16B, 16C, and16D) is within a predetermined range, and flows into the secondbranching unit 6. Subsequently, this refrigerant merges with therefrigerant that has passed through the indoor unit D that was about toperform heating.

The refrigerant that has flowed out from the second branching unit 6passes through the second indoor unit side connecting pipings 16 b and16 c and flows into each of the respective indoor units B and C. Then,the refrigerant that has flowed into each of the indoor units B and C isdecompressed to low pressure in the corresponding flow control valves11B and 11C, exchanges heat in the indoor unit side heat exchangers 10Band 10C with the indoor air, and is evaporated and gasified to cool theindoor space. Note that the opening degree of each of the flow controlvalves 11B and 11C is controlled on the basis of the amount of superheatat the outlet of the indoor unit side heat exchangers 10B, 10C, and 10D,respectively. Then, this refrigerant that has turned into a gaseousstate passes through the first indoor unit side connecting pipings 15Band 15C, the solenoid valves 13B and 13C, the first branching unit 5,the first heat source unit side connecting piping 15A, the first checkvalve 4 a, and the four-way valve 2, and is sucked into the compressor1.

During the cooling main operation, since the solenoid valves 13B and 13Care opened, and the solenoid valves 14B and 14C are closed, in the firstindoor unit side connecting pipings 15B and 15C, the second indoor unitside connecting pipings 16B and 16C, and the indoor units B and C therefrigerant flows in the direction of the solid arrows, and cooling isperformed. Further, since the solenoid valve 13D is closed and thesolenoid valve 14D is opened, in the first indoor unit side connectingpiping 15D, the second indoor unit side connecting piping 16D, and theindoor unit D, the refrigerant flows in the direction of the solidarrows, and heating is performed. Further, since the first heat sourceunit side connecting piping 15A is low in pressure, the second heatsource unit side connecting piping 16A is high in pressure, the endconnection of the heat source side heat exchanger 3 to the switchingvalve 4 is high in pressure, and the end connection of the four-wayvalve 2 to the switching valve 4 is low in pressure, the refrigerantinevitably flows to the first check valve 4 a and the fourth check valve4 d.

<Heat Exchange Capacity Control Method of Heat Source Side HeatExchanger 3>

Next, the heat exchange capacity control method of the heat source sideheat exchanger 3 will be described.

First, the object of controlling the heat exchange capacity of the heatsource side heat exchanger 3 (more specifically, the capacity of theheat source side heat exchanger 3 and the air volume of the air-sendingdevice 18) will be described.

To begin with, a case in which the air-conditioning apparatus ofEmbodiment 1 is in cooling only operation will be described. Normally,the capacity of the heat source side heat exchanger 3 and the air volumeof the air-sending device 18 are designed such that the air volume ofthe air-sending device 18 is to be driven at full speed when the outdoorair temperature is high, and the difference between the outdoor airtemperature and the condensing temperature is to be about 10 degrees C.,for example. In a case where the outdoor air temperature is low, if thecapacities of the heat source side heat exchanger 3 and the air-sendingdevice 18 are controlled in the same manner as in the case where theoutdoor air temperature is high, the condensing temperature will be at atemperature 10 degrees C. plus the outdoor air temperature. Thus,compared to the case where the outdoor air temperature is high, thecondensing temperature becomes substantially low, and the condensingpressure of the refrigeration cycle also becomes low.

As a result, the pressure difference between the outlet and the inlet ofeach of the flow control valves 11B, 11C, and 11D becomes small, and theopening degree of each of the flow control valves 11B, 11C, and 11Dneeds to be increased. The opening degree of each of the flow controlvalves 11B, 11C, and 11D is finite and cannot be made larger than acertain degree. If the opening degree needs to be made larger than theupper limit, a flow control valve that has a larger capacity needs to beselected. However, in such a case, the flow control valves 11B, 11C, and11D becomes large-sized and the variation of flow rate per a minimumopening width becomes large, thus fine control cannot be performed.

Accordingly, the condensing pressure of the refrigeration cycle needs tobe controlled so that it does not become excessively low by controllingthe heat exchange capacity of the heat source side heat exchanger 3(capacities of the heat source side heat exchanger 3 and the air-sendingdevice 18) such that the condensing temperature becomes a predeterminedvalue.

Next, a case in which the air-conditioning apparatus of Embodiment 1 isin heating only operation will be described. Normally, the capacity ofthe heat source side heat exchanger 3 and the air volume of theair-sending device 18 are designed such that the air volume of theair-sending device 18 is to be driven at full speed when the outdoor airtemperature is low. In a case where the outdoor air temperature is high,if the capacities of the heat source side heat exchanger 3 and theair-sending device 18 are controlled in the same manner as in the casewhere the outdoor air temperature is low, the evaporating temperaturebecomes substantially high, and the evaporating pressure of therefrigeration cycle also becomes high.

As a result, the pressure difference between the outlet and the inlet ofeach of the flow control valves 11B, 11C, and 11D becomes small, and theopening degree of each of the flow control valves 11B, 11C, and 110needs to be increased. The opening degree of each of the flow controlvalves 11B, 11C, and 11D is finite and cannot be made larger than acertain degree. If the opening degree needs to be made larger than theupper limit, a flow control valve that has a larger capacity needs to beselected. However, in such a case, the flow control valves 11B, 11C, and11D becomes large-sized and the variation of flow rate per a minimumopening width becomes large, thus fine control cannot be performed.

Accordingly, the evaporating pressure of the refrigeration cycle needsto be controlled so that it does not become excessively high bycontrolling the heat exchange capacity of the heat source side heatexchanger 3 (capacities of the heat source side heat exchanger 3 and theair-sending device 18) such that the evaporating temperature becomes apredetermined value.

Next, a case in which the air-conditioning apparatus of Embodiment 1 isin cooling main operation will be described. Normally, the capacity ofthe heat source side heat exchanger 3 and the air volume of theair-sending device 18 are designed such that, during the cooling onlyoperation, the air volume of the air-sending device 18 is to be drivenat full speed when the outdoor air temperature is high, and thedifference between the outdoor air temperature and the condensingtemperature is to be about 10 degrees C., for example. Normally, theoutdoor air temperature is low since a heating load is generated in thecooling main operation. During the cooling main operation, if thecapacities of the heat source side heat exchanger 3 and the air-sendingdevice 18 are controlled in the same manner as in the case where theoutdoor air temperature is high during the cooling only operation, thecondensing temperature is reduced by the amount of the outdoortemperature drop and further by the amount of condensation in theheating indoor unit D. Accordingly, the capacity of the heating indoorunit D becomes insufficient. Hence, the heat exchange capacity of theheat source side heat exchanger 3 (capacities of the heat source sideheat exchanger 3 and the air-sending device 18) needs to be controlledsuch that the condensing temperature becomes a predetermined value.

Next, a case in which the air-conditioning apparatus of Embodiment 1 isin heating main operation will be described. Normally, the capacity ofthe heat source side heat exchanger 3 and the air volume of theair-sending device 18 are designed such that, during the heating onlyoperation, the air volume of the air-sending device 18 is to be drivenat full speed when the outdoor air temperature is low. Normally, theoutdoor air temperature is relatively high since a cooling load isgenerated in the heating main operation. During the heating mainoperation, if the capacities of the heat source side heat exchanger 3and the air-sending device 18 are controlled in the same manner as inthe case where the outdoor air temperature is low during the heatingonly operation, the evaporating temperature is increased by the amountof the outdoor temperature rise and further by the amount of evaporationin the cooling indoor unit D. Accordingly, the capacity of the coolingindoor unit D becomes insufficient. Hence, the heat exchange capacity ofthe heat source side heat exchanger 3 (capacities of the heat sourceside heat exchanger 3 and the air-sending device 18) needs to becontrolled such that the evaporating temperature becomes a predeterminedvalue.

Accordingly, in the air-conditioning apparatus according to Embodiment1, a heat exchange capacity regulating device 152 controls the heatexchange capacity of the heat source side heat exchanger 3 as below.

FIG. 5 is a diagram illustrating a control content of the heat exchangecapacity regulating device of the air-conditioning apparatus as anexample of the refrigeration cycle apparatus of Embodiment 1 of theinvention. The heat exchange capacity regulating device 152 controls theair volume (capacity) of the air-sending device 18, the opening/closingof the solenoid valves 3 a, 3 b, 3 c, and 3 d, and the opening degree ofthe flow control valve 40 on the basis of the detection temperature ofthe condensing temperature detection device 19 and the evaporatingtemperature detection device 20.

Specifically, the heat exchange capacity of the heat source side heatexchanger 3 is controlled by four steps described below.

A first stage corresponds to a case in which the heat source side heatexchanger 3 is required to have the largest heat exchange capacity. Byopening the solenoid valves 3 a, 3 b, 3 c, and 3 d and closing the flowcontrol valve 40, the refrigerant is distributed to the first and secondrefrigerant circuits 21 and 22 and no refrigerant is distributed to thethird refrigerant circuit 23. That is, the refrigerant is distributed toboth the first heat exchanger 24 and the second heat exchanger 25 and norefrigerant is distributed to the third refrigerant circuit 23. Further,the air volume of the air-sending device 18 is controlled by an inverteror the like (not illustrated) between minimum air volume and full speed.

In a case where there is outside wind, such as building-induced wind,even if the air-sending device 18 is set to its minimum air volume, aconsiderably large amount of heat will be exchanged. Accordingly, if theheat source side heat exchanger 3 is a condenser, the condensingtemperature drops, and if an evaporator, the evaporating temperaturerises. Further, in a case where there is no outside wind, if thetemperature difference between the outdoor air temperature and thecondensing temperature or the evaporating temperature of the refrigerantin the heat source side heat exchanger 3 is large, the condensingtemperature drops or the evaporating temperature rises since a heatexchange capacity below the amount of heat exchange by free convectioncannot be obtained.

A second stage corresponds to a case in which the heat source side heatexchanger 3 is required to have the second largest heat exchangecapacity next to the first stage. In the second stage, the solenoidvalves 3 a and 3 c are opened, the solenoid valves 3 b and 3 d areclosed, and the flow control valve 40 is closed. As such, therefrigerant is distributed only to the first refrigerant circuit 23 andno refrigerant is distributed to the second refrigerant circuit 22 andthe third refrigerant circuit 23. That is, the refrigerant is onlydistributed to the first heat exchanger 24 and no refrigerant isdistributed to the second heat exchanger 25 and the third refrigerantcircuit 23 to substantially reduce the heat transfer area of the heatsource side heat exchanger 3. Further, the air volume of the air-sendingdevice 18 is controlled by an inverter or the like (not illustrated)between minimum air volume and full speed.

In this case, the amount of heat exchange by the outside wind, such as abuilding-induced wind, is substantially reduced, and the amount of heatexchange by free convection when there is no outside wind issubstantially reduced. Accordingly, when the heat source side heatexchanger 3 is a condenser, the drop in condensing temperature becomessmall, and when an evaporator, the rise in evaporating temperaturebecomes small.

A third stage corresponds to a case in which the heat source side heatexchanger 3 is required to have a smaller heat exchange capacity thanthat of the second stage. In the third stage, the solenoid valves 3 aand 3 c are opened, the solenoid valves 3 b and 3 d are closed, and theflow control valve 40 is controlled. As such, the refrigerant isdistributed to the first refrigerant circuit 21 and the thirdrefrigerant circuit 23 and no refrigerant is distributed to the secondrefrigerant circuit 22. That is, the refrigerant is distributed to boththe first heat exchanger 24 and the third refrigerant circuit 23 and norefrigerant is distributed to the second heat exchanger 25. Further, theair volume of the air-sending device 18 is controlled by an inverter orthe like (not illustrated) between minimum air volume and full speed. Atthis time, by controlling the opening degree of the flow control valve40, the amount of refrigerant distributed in the second refrigerantcircuit 23 can be continuously controlled and the heat exchange capacityof the heat source side heat exchanger 3 (more specifically, the firstheat exchanger 24) can be continuously controlled.

In this case, the amount of heat exchange by the outside wind, such as abuilding-induced wind, is further reduced from the second stage and theamount of heat exchange by free convection when there is no outside windis reduced in the same manner. Accordingly, when the heat source sideheat exchanger 3 is a condenser, the drop in condensing temperaturebecomes further small, and when an evaporator, the rise in evaporatingtemperature becomes further small.

A fourth stage corresponds to a case in which the heat source side heatexchanger 3 is required to have the smallest heat exchange capacity. Byfully opening the flow control valve 40 and closing the solenoid valves3 a, 3 b, 3 c, and 3 d, there will be no heat exchange in the heatsource side heat exchanger 3.

Note that in Embodiment 1, in the second stage, the refrigerant passageof the second heat exchanger 25 is closed (closing the solenoid valves 3b and 3 d), and in the fourth stage, the refrigerant passage of thefirst heat exchanger 24 is closed (closing the solenoid valves 3 a and 3c). Not to limited to the above, in the second stage, the refrigerantpassage of the first heat exchanger 24 may be closed (closing thesolenoid valves 3 a and 3 c), and in the fourth stage, the refrigerantpassage of the second heat exchanger 25 may be closed (closing thesolenoid valves 3 b and 3 d).

Next, the continuity of control by the heat exchange capacity regulatingdevice 152 in the first stage, the second stage, the third stage, andthe fourth stage will be described. Even if there is outside wind, thefirst stage and the second stage can be continuously controlled oncondition that (the capacity AK2 _(MAX) of the heat source unit sideheat exchanger when the heat source unit side air-sending device 18 inthe second stage is run at full speed) is larger than (the capacity AK1_(MAX) of the heat source unit side heat exchanger when the heat sourceunit side air-sending device 18 in the first stage is run at minimum airvolume), that is, when the wind velocity of the outside air allows AK2_(MAX)>AK1 _(MAX).

Similarly, even if there is outside wind, the second stage and the thirdstage can be continuously controlled on condition that (the capacity AK3_(MAX) of the heat source unit side heat exchanger when the heat sourceunit side air-sending device 18 in the third stage is run at full speed)is larger than (the capacity AK2 _(MAX) of the heat source unit sideheat exchanger when the heat source unit side air-sending device 18 inthe second stage is run at minimum air volume), that is, when the windvelocity of the outside air allows AK3 _(MAX)>AK2 _(MAX).

In Embodiment 1, the increase and decrease in the amount of refrigerantflowing in the third refrigerant circuit 23 can be continuouslycontrolled. Thus, by reducing the amount of refrigerant flowing in thesecond refrigerant circuit 23, the capacity AK3 _(MAX) of the heatsource unit side heat exchanger when the heat source unit sideair-sending device 18 in the third stage is run at full speed can beincreased. Therefore, compared to conventional air-conditioningapparatuses, continuous control of shifting from the second stage to thethird stage is facilitated.

As above, by controlling the bypass flow rate of the heat source sideheat exchanger 3 (the flow rate of the refrigerant flowing in the thirdrefrigerant circuit 23) and by controlling the heat exchange capacity ofthe heat source side heat exchanger 3 in four stages, even if there is acertain amount of outside wind, the heat exchange capacity of the heatsource side heat exchanger 3 can be continuously controlled. That is,when the heat source side heat exchanger 3 is a condenser, thecondensing temperature can be controlled to be at a predetermined valueor within a predetermined range, and when an evaporator, the evaporatingtemperature can be controlled to be at a predetermined value or within apredetermined range.

Note that distribution of the refrigerant to the third refrigerantcircuit 23 is not limited to the stages mentioned above. For example,the refrigerant may be distributed to the third refrigerant circuit 23in the first stage. By distributing the refrigerant to the thirdrefrigerant circuit 23 in the first stage, the capacity AK1 _(MAX) ofthe heat source unit side heat exchanger when the heat source unit sideair-sending device 18 in the first stage is run at minimum air volume isreduced. This capacity AK1 _(MAX) of the heat source unit side heatexchanger becomes smaller, the larger the refrigerant flow rate to thethird refrigerant circuit 23 becomes. Accordingly, compared toconventional air-conditioning apparatuses, continuous control ofshifting from the second stage to the third stage can be carried out.Therefore, compared to conventional air-conditioning apparatuses,continuous control of shifting from the first stage to the second stageis facilitated.

Next, the control content of the heat exchange capacity regulatingdevice 152 when the heat source side heat exchanger 3 is a condenserwill be described with the flowchart in FIG. 6.

FIG. 6 is a diagram illustrating a control flow of the heat exchangecapacity regulating device when the heat source side heat exchanger ofthe air-conditioning apparatus is functioning as a condenser as anexample of the refrigeration cycle apparatus of Embodiment 1 of theinvention.

In step 160, (a detection temperature TC of the condensing temperaturedetection device 19) and (a prescribed first target condensingtemperature TC1) are compared. If TC>TC1, control proceeds to step 161.In step 161, whether the air-sending device 18 is at full speed or notis determined. If the air-sending device 18 is not at full speed, thecontrol proceeds to step 162 and increases the air volume, and thenreturns to step 160. If the air-sending device 18 is at full speed, instep 163, the opening/closing of each of the solenoid valves 3 a and 3 cis determined. If the solenoid valves 3 a and 3 c are closed, in step164, the solenoid valves 3 a and 3 c are opened to open the firstrefrigerant circuit 21, that is, the first heat exchanger 24, and thenthe control returns to step 160. If the solenoid valves 3 a and 3 c areopened, the control proceeds to step 165.

In step 165, the opening degree of the flow control valve 40 isdetermined. If the flow control valve 40 is not totally closed, in step166, the opening degree of the flow control valve 40 is reduced, andthen the control returns to step 160. If the opening degree of the flowcontrol valve 40 is totally closed, the control proceeds to step 167. Instep 167, the opening/closing of each of the solenoid valves 3 b and 3 dis determined. If the solenoid valves 3 b and 3 d are closed, in step168, the solenoid valves 3 b and 3 d are opened to open the secondrefrigerant circuit 22, that is, the second heat exchanger 25, and thenthe control returns to step 160. If the solenoid valves 3 b and 3 d areopened, the control also returns to step 160.

On the other hand, if TC≦TC1 is determined in step 160, the controlproceeds to step 170. In step 170, (a detection temperature TC of thecondensing temperature detection device 19) and (a prescribed secondtarget condensing temperature TC2 that is set smaller than the firsttarget condensing temperature) are compared. If TC<TC2, the controlproceeds to step 171, and if TC≦TC2, the control returns to step 160. Instep 171, whether the air-sending device 18 is set to minimum air volumeor not is determined. If the air-sending device 18 is not set to minimumair volume, the control proceeds to step 172 and decreases the airvolume, and then returns to step 160. If the air-sending device 18 isset to minimum air volume, in step 173, the opening/closing of each ofthe solenoid valves 3 b and 3 d is determined. If the solenoid valves 3b and 3 d are opened, in step 174, the solenoid valves 3 b and 3 d areclosed to close the second refrigerant circuit 22, that is, the secondheat exchanger 25, and then the control returns to step 160. If thesolenoid valves 3 b and 3 d are closed, the control proceeds to step175.

In step 175, the opening degree of the flow control valve 40 isdetermined. If the flow control valve 40 is not fully opened, in step176, the opening degree of the flow control valve 40 is increased, andthen the control returns to step 160. If the opening degree of the flowcontrol valve 40 is fully opened, the control proceeds to step 177. Instep 177, the opening/closing of each of the solenoid valves 3 a and 3 cis determined. If the solenoid valves 3 a and 3 c are opened, in step178, the solenoid valves 3 a and 3 c are closed to close the firstrefrigerant circuit 21, that is, the first heat exchanger 24, and thenthe control returns to step 160. In step 177, if the solenoid valves 3 aand 3 c are closed, the control also returns to step 160.

With the above, the detection temperature TC of the condensingtemperature detection device 19 can be controlled to a temperaturebetween the first target condensing temperature TC1 and the secondtarget condensing temperature TC2.

Next, the control content of the heat exchange capacity regulatingdevice 152 when the heat source side heat exchanger 3 is an evaporatorwill be described with the flowchart in FIG. 7.

FIG. 7 is a diagram illustrating a control flow of a heat exchangecapacity regulating device when the heat source side heat exchanger ofan air-conditioning apparatus is functioning as an evaporator as anexample of a refrigeration cycle apparatus of Embodiment 1 of theinvention. In step 180, (a detection temperature TE of the evaporatingtemperature detection device 20) and (a prescribed first targetevaporating temperature TE1) are compared. If TE<TE1, control proceedsto step 181. In step 181, whether the air-sending device 18 is at fullspeed or not is determined. If the air-sending device 18 is not at fullspeed, the control proceeds to step 182 and increases the air volume,and then returns to step 180. If the air-sending device 18 is at fullspeed, in step 183, the opening/closing of each of the solenoid valves 3a and 3 c is determined. If the solenoid valves 3 a and 3 c are closed,in step 184, the solenoid valves 3 a and 3 c are opened to open thefirst refrigerant circuit 21, that is, the first heat exchanger 24, andthen the control returns to step 180. If the solenoid valves 3 a and 3 care opened, the control proceeds to step 185.

In step 185, the opening degree of the flow control valve 40 isdetermined. If the flow control valve 40 is not totally closed, in step186, the opening degree of the flow control valve 40 is reduced, andthen the control returns to step 180. If the opening degree of the flowcontrol valve 40 is totally closed, the control proceeds to step 187. Instep 187, the opening/closing of each of the solenoid valves 3 b and 3 dis determined. If the solenoid valves 3 b and 3 d are closed, in step188, the solenoid valves 3 b and 3 d are opened to open the secondrefrigerant circuit 22, that is, the second heat exchanger 25, and thenthe control returns to step 180. If the solenoid valves 3 b and 3 d areopened, the control also returns to step 180.

On the other hand, if TE≧TE1 is determined in step 180, the controlproceeds to step 190. In step 190, (a detection temperature TE of theevaporating temperature detection device 20) and (a prescribed secondtarget evaporating temperature TE2 that is set larger than the firsttarget condensing temperature) are compared. If TE>TE2, the controlproceeds to step 191, and if TE≦TE2, the control returns to step 180. Instep 191, whether the air-sending device 18 is set to minimum air volumeor not is determined. If the air-sending device 18 is not set to minimumair volume, the control proceeds to step 192 and decreases the airvolume, and then returns to step 180. If the air-sending device 18 isset to minimum air volume, in step 193, the opening/closing of each ofthe solenoid valves 3 b and 3 d is determined. If the solenoid valves 3b and 3 d are opened, in step 194, the solenoid valves 3 b and 3 d areclosed to close the second refrigerant circuit 22, that is, the secondheat exchanger 25, and then the control returns to step 180. If thesolenoid valves 3 b and 3 d are closed, the control proceeds to step195.

In step 195, the opening degree of the flow control valve 40 isdetermined. If the flow control valve 40 is not fully opened, in step196, the opening degree of the flow control valve 40 is increased, andthen the control returns to step 180. If the opening degree of the flowcontrol valve 40 is fully opened, the control proceeds to step 197. Instep 197, the opening/closing of each of the solenoid valves 3 a and 3 cis determined. If the solenoid valves 3 a and 3 c are opened, in step198, the solenoid valves 3 a and 3 c are closed to close the firstrefrigerant circuit 21, that is, the first heat exchanger 24, and thenthe control returns to step 180. In step 197, if the solenoid valves 3 aand 3 c are closed, the control also returns to step 180.

With the above, the detection temperature TE of the evaporatingtemperature detection device 20 can be controlled to a temperaturebetween the first target evaporating temperature TE1 and the secondtarget evaporating temperature TE2.

With the air-conditioning apparatus of the above configuration, even ina case in which the control range of the air volume of the air-sendingdevice 18 cannot be continuously controlled from full speed to stop, bycontrolling the flow rate of the refrigerant flowing in the thirdrefrigerant circuit 23, the heat exchange capacity of the heat sourceside heat exchanger 3 can be continuously controlled.

Further, unlike conventional air-conditioning apparatuses, the number ofheat exchangers constituting the heat source side heat exchanger 3 doesnot have to be increased in order to reduce the difference between eachheat exchange capacity of the heat source side heat exchanger 3 in eachstage. Accordingly, increase in the number of solenoid valves and thelike that is required to open/close the refrigerant passage to each heatexchanger constituting the heat source side heat exchanger 3 can beavoided.

Note that as illustrated in FIG. 8, a distributor 30 that regulates thegas-to-liquid ratio of the two-phase gas-liquid refrigerant to aprescribed ratio (for example, equal) and that sends out the refrigerantdownstream may be provided to a junction of the first refrigerantcircuit 21, second refrigerant circuit 22, and the third refrigerantcircuit 23, in which the junction is the junction on the inlet side whenthe heat source side heat exchanger 3 is an evaporator. In theair-conditioning apparatus configured as above, when the heat sourceside heat exchanger 3 operates as an evaporator, even with a flow of alow-pressure two-phase gas-liquid refrigerant, the refrigerant can bedistributed with, for example, an equal gas-to-liquid ratio to eachrefrigerant circuits (the first refrigerant circuit 21, the secondrefrigerant circuit 22, and the third refrigerant circuit 23).Accordingly, a refrigerant with an excessively high gas ratio or, on theother hand, a refrigerant with an excessively high liquid ratio flowinginto the heat source side heat exchanger 3, and, consequently, renderingthe heat exchange capacity of the heat source side heat exchanger 3 tobe unstable can be prevented. That is, an advantageous effect isobtained in which the heat exchange capacity of the heat source sideheat exchanger 3 can be controlled in a stable manner.

Further, although in Embodiment 1, the refrigerant that is used has notbeen mentioned in particular, a refrigerant that, when heating theobject to be heat exchanged (air, water, or the like) in the condenser,heats the object to be heat exchanged in a supercritical state withoutcondensing may be used. By using such a refrigerant, the gas-liquidseparator 7 will not be needed to be provided in the refrigerant circuitof the air-conditioning apparatus. Accordingly, an advantageous effectin which an efficient operation of the air-conditioning apparatus duringthe cooling main operation can be obtained without increasing pressureloss in the heating indoor unit and decreasing the heating capacity.

Furthermore, the air-conditioning apparatus shown in Embodiment 1 ismerely an example. For example, the heat source unit A and the relayunit E may be a single unit (the components of the heat source unit Aand the components of the relay unit E may be disposed in a singularhousing). The air-conditioning apparatus may be one that is capable ofperforming only the cooling only operation or the heating onlyoperation, for example. In this case, the four-way valve 2 and theswitching valve 4 will not be needed to be provided in the heat sourceunit A. For example, the air-conditioning apparatus may be one with asingle indoor unit rather than a multi-room air-conditioning systemhaving a plurality of indoor units.

Furthermore, it goes without saying that the refrigeration cycleapparatus of the invention can be employed to a device other than theair-conditioning apparatus. For example, the refrigeration cycleapparatus according to the invention can be employed to a hot waterstorage hot water device and the like.

Embodiment 2

When using a heat source side heat exchanger 3 with a plurality of heatexchangers connected in parallel as a condenser, there are cases inwhich the density of the refrigerant that is flowing in the heat sourceside heat exchanger becomes high, resulting in drop of flow velocity.This raises a concern of drop of the heat transfer coefficient of therefrigerant (the heat exchange efficiency of the heat source side heatexchanger 3). By adding the below configuration, this matter of concerncan be resolved, and a further efficient air-conditioning apparatus canbe obtained. Note that in Embodiment 2, elements not stated inparticular is the same as Embodiment 1.

FIG. 9 is a diagram illustrating a refrigerant circuit of anair-conditioning apparatus as an example of a refrigeration cycleapparatus of Embodiment 2 of the invention.

The air-conditioning apparatus according to Embodiment 2 is one with abypass piping 50 and a solenoid valve 51 added to the configuration ofthe air-conditioning apparatus of Embodiment 1.

The bypass piping 50 serially connects the first heat exchanger 24 andthe second heat exchanger 25. One end of this bypass piping 50 isconnected to the second refrigerant circuit 22 between the second heatexchanger 25 and the solenoid valve 3 d. Further, the other end of thisbypass piping 50 is connected to the first refrigerant circuit 21between the first heat exchanger 24 and the solenoid valve 3 a. Thesolenoid valve 51 is provided in the bypass piping 50 and opens andcloses the refrigerant passage of the bypass piping 50.

The bypass piping 50 corresponds to the connecting piping of theinvention. Further, the solenoid valve 51 corresponds to the on-offdevice of the invention. Note that although in Embodiment 2, a devicewith a valve structure is employed as the on-off device, Embodiment 2 isnot limited to the device. The structure of the on-off device may be anythat can open/close the refrigerant passage of the bypass piping 50.

Next, the heat exchange capacity control method of the heat source sideheat exchanger 3 will be described. In the air-conditioning apparatusaccording to Embodiment 2, the heat exchange capacity of the heat sourceside heat exchanger 3 is controlled in five stages when the heat sourceside heat exchanger 3 operates as a condenser (during the cooling onlyoperation and the cooling main operation).

A first stage corresponds to a case in which the heat source side heatexchanger 3 is required to have the largest heat exchange capacity. Thesolenoid valves 3 b and 3 c are opened, the solenoid valves 3 a and 3 dand the flow control valve 40 are closed. Further, the solenoid valve 51is opened. With the above, the refrigerant is distributed through thesecond heat exchanger 25 and the first heat exchanger 24 in this orderand no refrigerant is distributed in the third refrigerant circuit 23.Further, the air volume of the air-sending device 18 is controlled by aninverter or the like (not illustrated) between minimum air volume andfull speed.

In FIG. 10, a refrigerant flow in the heat source side heat exchanger 3during the cooling only operation is described as an example of therefrigerant flow in the heat source side heat exchanger 3 in the firststage.

A high-temperature high-pressure gas refrigerant that has beendischarged from the compressor 1 flows into the four-way valve 2. Therefrigerant that has flowed out of the four-way valve 2 flows into theheat source side heat exchanger 3. The high-temperature high-pressuregas refrigerant that has flowed into the heat source side heat exchanger3 flows into the second heat exchanger 25, first. This refrigerantpasses through the bypass piping 50 and flows into the first heatexchanger 24. Subsequently, the refrigerant that has flowed out of thefirst heat exchanger 24 passes through the fourth check valve 4 d andflows into the second heat source unit side connecting piping 16A. Thehigh-temperature high-pressure gas refrigerant that has flowed into theheat source side heat exchanger 3 exchanges heat with air sent by theair-sending device 18 and is condensed and liquefied in the course offlowing into the second heat exchanger 25 and flowing out of the firstheat exchanger 24.

Note that the refrigerant flow after the second heat source unit sideconnecting piping 16A is the same as that described in Embodiment 1, anddescription will be omitted here.

In a case of the first stage, if there is outside wind, such asbuilding-induced wind, even if the air-sending device 18 is set to itsminimum air volume, a considerably large amount of heat will beexchanged. Further, if the heat source side heat exchanger 3 is acondenser, the condensing temperature drops, and if an evaporator, theevaporating temperature rises. Thus, the heat exchange capacity of theheat source side heat exchanger 3 is controlled with a similar controlmethod as that of Embodiment 1 after the first stage. That is, the firststage to the fourth stage described in Embodiment 1 is a second stage toa fifth stage of Embodiment 2.

In more detail, the control method of the heat exchange capacity of theheat source side heat exchanger 3 according to Embodiment 2 is as shownin FIG. 11.

FIG. 11 is a diagram illustrating a control flow of the heat exchangecapacity regulating device when the heat source side heat exchanger ofthe air-conditioning apparatus is functioning as a condenser as anexample of the refrigeration cycle apparatus of Embodiment 2 of theinvention.

In step 160, (a detection temperature TC of the condensing temperaturedetection device 19) and (a prescribed first target condensingtemperature TC1) are compared. If TC>TC1, control proceeds to step 161.In step 161, whether the air-sending device 18 is at full speed or notis determined. If the air-sending device 18 is not at full speed, thecontrol proceeds to step 162 and increases the air volume, and thenreturns to step 160. If the air-sending device 18 is at full speed, instep 163, the opening/closing of each of the solenoid valves 3 a and 3 cis determined. If the solenoid valves 3 a and 3 c are closed, in step164, the solenoid valves 3 a and 3 c are opened to open the firstrefrigerant circuit 21, that is, the first heat exchanger 24, and thenthe control returns to step 160. If the solenoid valves 3 a and 3 c areopened, the control proceeds to step 165.

In step 165, the opening degree of the flow control valve 40 isdetermined. If the flow control valve 40 is not totally closed, in step166, the opening degree of the flow control valve 40 is reduced, andthen the control returns to step 160. If the opening degree of the flowcontrol valve 40 is totally closed, the control proceeds to step 167. Instep 167, the opening/closing of each of the solenoid valves 3 b and 3 dis determined. If the solenoid valves 3 b and 3 d are closed, in step168, the solenoid valves 3 b and 3 d are opened to open the secondrefrigerant circuit 22, that is, the second heat exchanger 25, and thenthe control returns to step 160. If the solenoid valves 3 b and 3 d areopened, the control proceeds to step 200.

In step 200, the opening/closing of the solenoid valve 51 is determined.If the solenoid valve 51 is closed, in step 201, the solenoid valves 3 aand 3 d are closed, and in step 202, the solenoid valve 51 is opened,and then the control returns to step 160. That is, the refrigerantpassage is opened so that the second heat exchanger 25 and the firstheat exchanger 24 are serially connected, and the control returns tostep 160. If the solenoid valve 51 is opened, the control also returnsto step 160.

On the other hand, if TC≦TC1 is determined in step 160, the controlproceeds to step 170. In step 170, (a detection temperature TC of thecondensing temperature detection device 19) and (a prescribed secondtarget condensing temperature TC2 that is set smaller than the firsttarget condensing temperature) are compared. If TC<TC2, the controlproceeds to step 171, and if TC≧TC2, the control returns to step 160. Instep 171, whether the air-sending device 18 is set to minimum air volumeor not is determined. If the air-sending device 18 is not set to minimumair volume, the control proceeds to step 172 and decreases the airvolume, and then returns to step 160. If the air-sending device 18 isset to minimum air volume, the control proceeds to step 210.

In step 210, the opening/closing of the solenoid valve 51 is determined.If the solenoid valve 51 is opened, in step 211, the solenoid valves 3 aand 3 d are opened, and in step 212, the solenoid valve 51 is closed,and then the control returns to step 160. That is, the refrigerantpassage is opened so that the second heat exchanger 25 and the firstheat exchanger 24 are parallelly connected, and the control returns tostep 160. If the solenoid valve 51 is closed, the control proceeds tostep 173.

In step 173, the opening/closing of each of the solenoid valves 3 b and3 d is determined. If the solenoid valves 3 b and 3 d are opened, instep 174, the solenoid valves 3 b and 3 d are closed to close the secondrefrigerant circuit 22, that is, the second heat exchanger 25, and thenthe control returns to step 160. If the solenoid valves 3 b and 3 d areclosed, the control proceeds to step 175.

In step 175, the opening degree of the flow control valve 40 isdetermined. If the flow control valve 40 is not fully opened, in step176, the opening degree of the flow control valve 40 is increased, andthen the control returns to step 160. If the opening degree of the flowcontrol valve 40 is fully opened, the control proceeds to step 177. Instep 177, the opening/closing of each of the solenoid valves 3 a and 3 cis determined. If the solenoid valves 3 a and 3 c are opened, in step178, the solenoid valves 3 a and 3 c are closed to close the firstrefrigerant circuit 21, that is, the first heat exchanger 24, and thenthe control returns to step 160. In step 177, if the solenoid valves 3 aand 3 c are closed, the control also returns to step 160.

With the above, the detection temperature TC of the condensingtemperature detection device 19 can be controlled to a temperaturebetween the first target condensing temperature TC1 and the secondtarget condensing temperature TC2.

Note that when the heat source side heat exchanger 3 operates as anevaporator (during the heating only operation and the heating mainoperation), the solenoid valve 51 is closed and the heat exchangecapacity of the heat source side heat exchanger 3 is controlled with asimilar method as that of Embodiment 1.

In the air-conditioning apparatus configured as above, the heat sourceside heat exchanger 3 operates as a condenser, and even with a flow of ahigh-pressure high-density refrigerant, by connecting the first heatexchanger 24 and the second heat exchanger 25 in series, thecross-sectional area of the passage of the refrigerant can be made smallcompared to when the first heat exchanger 24 and the second heatexchanger 25 is connected in parallel. Accordingly, the drop of flowvelocity of the refrigerant flowing in the heat source side heatexchanger 3 can be suppressed. Thus, the heat transfer coefficient ofthe refrigerant (the heat exchange efficiency of the heat source sideheat exchanger 3) is increased when the heat source side heat exchanger3 is used as a condenser.

Furthermore, when the density of the refrigerant flowing in the heatsource side heat exchanger 3 is low, that is, when the heat source sideheat exchanger is operated as a condenser, by connecting the first heatexchanger 24 and the second heat exchanger 25 in parallel, the increaseof flow velocity of the refrigerant flowing in the heat source side heatexchanger 3 can be suppressed. Accordingly, the pressure loss of therefrigerant flowing in the heat source side heat exchanger 3 can bereduced.

Hence, the efficiency of the air-conditioning apparatus is furtherimproved.

In addition, in the air-conditioning apparatus configured as above, airsent from the air-sending device flows into the second heat exchanger 25that is on the upstream side in the refrigerant flow direction afterflowing into the first heat exchanger 24 that is on the downstream sidein the refrigerant flow direction. Accordingly, the air that hasexchanged heat in the first heat exchanger 24 and that has increased itstemperature exchanges heat with the high-temperature refrigerant thathas flowed into the second heat exchanger 25 from the compressor 1.Thus, the heat transfer efficiency of the heat source side heatexchanger 3 is improved and the efficiency of the air-conditioningapparatus is improved.

Embodiment 3

Considering the effect of the toxicity of the refrigerant on the humanbody and its flammability, an acceptable concentration of refrigerantleakage in a space such as an indoor space is stipulated under aninternational standard. For example, each of the acceptableconcentration of refrigerant leakage in a space is determined as 0.44kg/m³ for R410A, which is a fluorocarbon refrigerant, 0.07 kg/m³ forCO₂, and 0.008 kg/m³ for propane.

In order to prevent such refrigerants leaking into indoor spaces, water,brine, and the like may be preferably distributed to indoor heatexchangers. Accordingly, it will be effective to embody the invention inan air-conditioning apparatus that distributes water, brine, and thelike to indoor heat exchangers. Note that in Embodiment 3, elements notstated in particular is the same as Embodiments 1 or 2.

FIG. 12 is a diagram illustrating a refrigerant circuit of anair-conditioning apparatus as an example of a refrigeration cycleapparatus of Embodiment 3 of the invention.

The air-conditioning apparatus according to Embodiment 3 is anair-conditioning apparatus in which water is distributed to the indoorheat exchangers. Further, this air-conditioning apparatus is amulti-room air-conditioning system connecting a plurality of indoorunits to a single heat source unit. This air-conditioning apparatusincludes the heat source unit A, a relay unit E′, and a plurality ofindoor units 71. In Embodiment 3, the air-conditioning apparatusincludes three indoor units 71 a, 71 b, and 71 c.

(Heat Source Unit A)

Same as Embodiment 1, the heat source unit A includes the compressor 1,the four-way valve 2, the heat source side heat exchanger 3, theair-sending device 18, which is capable of variably controlling thevolume of air and which sends air to the heat source side heat exchanger3, and the switching valve 4 that switches the passage of therefrigerant discharged from the compressor 1.

In the heat source unit A according to Embodiment 3, the fourth checkvalve 4 d is connected to a refrigerant piping between the firstbranching unit 5 and a solenoid valve 68 in the relay unit E′ to bedescribed below via the second heat source unit side connecting piping16A. Further, the first check valve 4 a is connected to the firstbranching unit 5 of the relay unit E′ to be described below via thefirst heat source unit side connecting piping 15A.

(Indoor Units 71)

The indoor units 71 a, 71 b, and 71 c each have the same configuration.

In more detail, the indoor unit 71 a includes an indoor side heatexchanger 70 a. One end of the indoor side heat exchanger 70 a isconnected to a first water switching valve 72 a of the relay unit E′ tobe described below via a third water piping 65 a. The other end of theindoor side heat exchanger 70 a is connected to the second waterswitching valve 73 a of the relay unit E′ to be described below via afourth water piping 66 a.

The indoor unit 71 a includes an indoor side heat exchanger 70 b. Oneend of the indoor side heat exchanger 70 b is connected to a first waterswitching valve 72 b of the relay unit E′ to be described below via athird water piping 65 b. The other end of the indoor side heat exchanger70 b is connected to the second water switching valve 73 b of the relayunit E′ to be described below via a fourth water piping 66 b.

The indoor unit 71 c includes an indoor side heat exchanger 70 c. Oneend of the indoor side heat exchanger 70 c is connected to a first waterswitching valve 72 c of the relay unit E′ to be described below via athird water piping 65 c. The other end of the indoor side heat exchanger70 c is connected to the second water switching valve 73 c of the relayunit E to be described below via a fourth water piping 66 c.

(Relay Unit E′)

The relay unit E′ includes the first branching unit 5, the secondbranching unit 6, the flow control valve 9, a first water-to-refrigerantheat exchanger 55B, a second water-to-refrigerant heat exchanger 55C, aplurality of first water switching valves 72 (the first water switchingvalves 72 a, 72 b, and 72 c), a plurality of second water switchingvalves 73 (the second water switching valves 73 a, 73 b, and 73 c), aplurality of pumps 60 (pumps 60A and 60B), and the solenoid valve 68.

The first branching unit 5 includes solenoid valves 13B and 13C and thesolenoid valves 14B and 14C.

One end of each of the solenoid valves 13B and 13C is connected to thefirst heat source unit side connecting piping 15A. Further, the otherend of solenoid valve 13B is connected to the first water-to-refrigerantheat exchanger 55B via a first water-to-refrigerant heat exchangerconnecting piping 63B. The other end of solenoid valve 13C is connectedto the second water-to-refrigerant heat exchanger 55C via a firstwater-to-refrigerant heat exchanger connecting piping 63C.

One end of each of the solenoid valves 14B and 14C is connected to thesecond branching unit 6. Further, the other end of solenoid valve 14B isconnected to the first heat source unit side connecting piping 15A via afirst water-to-refrigerant heat exchanger connecting piping 63B. Theother end of solenoid valve 14C is connected to the secondwater-to-refrigerant heat exchanger 55C via a first water-to-refrigerantheat exchanger connecting piping 63C.

The solenoid valve 68 is provided in the refrigerant piping between thesolenoid valves 14B and 14C and the second branching unit 6, and thesecond heat source unit side connecting piping 16A is connected to thispiping between the solenoid valves 14B and 14C and the solenoid valve68.

The second branching unit 6 branchingly connects secondwater-to-refrigerant heat exchanger connecting pipings 64B and 64C tothe second heat source unit side connecting piping 16A. This secondwater-to-refrigerant heat exchanger connecting piping 64B is connectedto the first water-to-refrigerant heat exchanger 55B and a flow controlvalve 11B is provided in the second water-to-refrigerant heat exchangerconnecting piping 64B. Further, the second water-to-refrigerant heatexchanger connecting piping 64 c is connected to the secondwater-to-refrigerant heat exchanger 55C and a flow control valve 11C isprovided in the second water-to-refrigerant heat exchanger connectingpiping 64C.

The flow control valve 9 is connected between the second branching unit6 and the first heat source unit side connecting piping 15A.

The first water-to-refrigerant heat exchanger 55B exchanges heat betweenthe refrigerant flowing in the heat source side refrigerant circuit onthe heat source unit A side and water flowing in the use siderefrigerant circuit on the indoor units 71 side. In this firstwater-to-refrigerant heat exchanger 55B, as described above, the firstwater-to-refrigerant heat exchanger connecting piping 63B and the secondwater-to-refrigerant heat exchanger connecting piping 64B is connectedas the heat source side refrigerant circuit. Further, in this firstwater-to-refrigerant heat exchanger 55B, a first water piping 61B and asecond water piping 62B is connected as the use side refrigerantcircuit.

Furthermore, the first water piping 61B is also connected to the secondwater switching valves 73 a, 73 b, and 73 c. The second water piping 62Bis connected to the second water switching valves 73 a, 73 b, and 73 c.

The pump 60 b that circulates the water in the use side refrigerantcircuit is provided to the first water piping 61B.

The second water-to-refrigerant heat exchanger 55C exchanges heatbetween the refrigerant flowing in the heat source side refrigerantcircuit on the heat source unit A side and water flowing in the use siderefrigerant circuit on the indoor units 71 side. In this firstwater-to-refrigerant heat exchanger 55C, as described above, the firstwater-to-refrigerant heat exchanger connecting piping 63C and the secondwater-to-refrigerant heat exchanger connecting piping 64C is connectedas the heat source side refrigerant circuit. Further, in this firstwater-to-refrigerant heat exchanger 55C, a first water piping 61C and asecond water piping 62C is connected as the use side refrigerantcircuit.

Furthermore, the first water piping 61C is also connected to the firstwater switching valves 72 a, 72 b, and 72 c. The second water piping 62Cis connected to the second water switching valves 73 a, 73 b, and 73 c.

The pump 60C that circulates the water in the use side refrigerantcircuit is provided to the first water piping 61C.

<Flow of Refrigerant>

The flow of the refrigerant of the air-conditioning apparatus accordingto Embodiment 3 will be subsequently described with reference to FIGS.13, 14, and 15. In FIG. 13, the refrigerant flows during the coolingonly operation and the refrigerant flow during the heating onlyoperation will be described. In FIG. 14, the refrigerant flow during theheating main operation will be described. In FIG. 15, the refrigerantflow during the cooling main operation will be described.

(Flow of Refrigerant During Cooling Only Operation)

FIG. 13 is a diagram illustrating flows of the refrigerant in therefrigerant circuit of the air-conditioning apparatus during the coolingoperation and the heating operation as an example of the refrigerationcycle apparatus of Embodiment 3 of the invention.

First, the flow of the refrigerant flowing in the heat source siderefrigerant circuit on the heat source unit A side will be described.The direction of the solid arrows in FIG. 13 indicates the direction ofthe refrigerant flow during the cooling only operation.

A high-temperature high-pressure gas refrigerant that has beendischarged from the compressor 1 flows into the four-way valve 2. Therefrigerant that has flowed out of the four-way valve 2 flows into theheat source side heat exchanger 3. The refrigerant that has flowed intothe heat source side heat exchanger 3 exchanges heat with the air sentby the air-sending device 18 and is condensed and liquefied. Thecondensed and liquefied, high-pressure liquid refrigerant flows throughthe fourth check valve 4 d, passes through the second heat source unitside connecting piping 16A, and the solenoid valve 68 in this order, andflows into the second branching unit 6. The high-pressure liquidrefrigerant that has flowed into the second branching unit 6 passesthrough the second water-to-refrigerant heat exchanger connectingpipings 64B and 64C and flows into each of the respective flow controlvalves 11B and 11C.

This refrigerant is decompressed to low pressure by the flow controlvalves 11B and 11C that are controlled based on the amount of superheatin the corresponding outlets of the first water-to-refrigerant heatexchanger 55B and the second water-to-refrigerant heat exchanger 55C.The refrigerant exchanges heat with water in the water-to-refrigerantheat exchangers 55B and 55C and is evaporated and gasified to cool thewater. Then, this refrigerant that has turned into a gaseous statepasses through the first water-to-refrigerant heat exchanger connectingpipings 63B and 63C, the solenoid valves 13B and 13C, the firstbranching unit 5, the first heat source unit side connecting piping 15A,the first check valve 4 a, and the four-way valve 2, and is sucked intothe compressor 1.

During the cooling only operation, the solenoid valve 68 is opened, thesolenoid valves 13B and 13C are opened, the solenoid valves 14B and 14Care closed. Accordingly, the refrigerant flows in the direction of thesolid arrows in the first water-to-refrigerant heat exchanger connectingpipings 63B and 63C, the second water-to-refrigerant heat exchangerconnecting pipings 64B and 64C, the first water-to-refrigerant heatexchanger 55B and the second water-to-refrigerant heat exchanger 55C.Further, since the first heat source unit side connecting piping 15A islow in pressure, the second heat source unit side connecting piping 16Ais high in pressure, the end connection of the heat source side heatexchanger 3 to the switching valve 4 is high in pressure, and the endconnection of the four-way valve 2 to the switching valve 4 is low inpressure, the refrigerant inevitably flows to the first check valve 4 aand the fourth check valve 4 d.

Next, the flow of water flowing in the use side refrigerant circuit onthe indoor units 71 side will be described. The direction of the solidarrows in FIG. 13 indicates the direction of the water flow during thecooling only operation.

Water that has been cooled in the first water-to-refrigerant heatexchanger 55B and second water-to-refrigerant heat exchanger 55C ispressurized in the respective pumps 60B and 60C, passes through thecorresponding first water pipings 61B and 61C, and is merged in each ofthe first water switching valves 72 a, 72 b, and 72 c. The water thathas been merged in the first water switching valves 72 a, 72 b, and 72 cpasses through the third water pipings 65 a, 65 b, and 65 c and flowsinto the indoor units 71 a, 71 b, and 71 c, respectively. The water thathas flowed into the indoor units 71 a, 71 b, and 71 c increases itstemperature while cooling the indoor air in the respective indoor sideheat exchangers 70 a, 70 b, and 70 c. The water that has been heated inthe indoor side heat exchangers 70 a, 70 b, and 70 c passes through thefourth water pipings 66 a, 66 b, and 66 c and flows into the secondwater switching valves 73 a, 73 b, and 73 c, respectively. The waterthat has flowed into the second water switching valves 73 a, 73 b, and73 c is each branched to the second water piping 62B and the secondwater piping 62C and returns to the first water-to-refrigerant heatexchanger 55B and the second water-to-refrigerant heat exchanger 55C,respectively.

(Flow of Refrigerant During Heating Only Operation)

First, the flow of the refrigerant flowing in the heat source siderefrigerant circuit on the heat source unit A side will be described.The direction of the broken-line arrows in FIG. 13 indicates thedirection of the refrigerant flow during the heating only operation.

A high-temperature high-pressure gas refrigerant that has beendischarged from the compressor 1 flows into the four-way valve 2. Therefrigerant that has flowed out of the four-way valve 2, passes throughthe third check valve 4 c, the second heat source unit side connectingpiping 16A, and flows into the first branching unit 5. Thehigh-temperature high-pressure gas refrigerant that has flowed into thefirst branching unit 5 passes through each of the solenoid valves 14Band 14C and the corresponding first water-to-refrigerant heat exchangerconnecting pipings 63B and 63C in this order and flows into the firstwater-to-refrigerant heat exchanger 55B and the secondwater-to-refrigerant heat exchanger 55C. Further, the high-temperaturehigh-pressure gas refrigerant that has flowed into the firstwater-to-refrigerant heat exchanger 55B and the secondwater-to-refrigerant heat exchanger 55C exchanges heat with water and iscondensed and liquefied to heat the water.

This refrigerant in a liquid state passes through the nearly fullyopened flow control valves 11B and 11C that are controlled based on theamount of subcooling in each of the respective outlet of the firstwater-to-refrigerant heat exchanger 55B and the secondwater-to-refrigerant heat exchanger 55C and flows into the respectivesecond water-to-refrigerant heat exchanger connecting pipings 64B and64C. The refrigerant flows into the second branching unit 6 and ismerged, and, further, passes through the third flow control valve 9. Therefrigerant is decompressed into a low-pressure two-phase gas-liquidstate in either of the flow control valves 11B and 11C or the third flowcontrol valve 9. Further, the refrigerant that has been decompressed tolow pressure passes through the first heat source unit side connectingpiping 15A and the second check valve 4 b of the heat source unit A andflows into the heat source side heat exchanger 3. The refrigerant thathas flowed into the heat source side heat exchanger 3 exchanges heatwith the air sent by the air-sending device 18, which is capable ofvariably controlling the volume of air, and is evaporated and gasified.The refrigerant that has turned into a gaseous state passes through thefour-way valve 2 of the heat source unit and is sucked into thecompressor 1.

During the heating only operation, the solenoid 68 is closed, thesolenoid valves 14B and 14C are opened, the solenoid valves 13B and 13Care closed. Accordingly, the refrigerant flows in the direction of thebroken-line arrows in the first water-to-refrigerant heat exchangerconnecting pipings 63B and 63C, the second water-to-refrigerant heatexchanger connecting pipings 64B and 64C, the first water-to-refrigerantheat exchanger 55B and the second water-to-refrigerant heat exchanger55C. Further, since the first heat source unit side connecting piping15A is low in pressure, the second heat source unit side connectingpiping 16A is high in pressure, the end connection of the heat sourceside heat exchanger 3 to the switching valve 4 is low in pressure, andthe end connection of the four-way valve 2 to the switching valve 4 ishigh in pressure, the refrigerant inevitably flows to the second checkvalve 4 b and the third check valve 4 c.

Next, the flow of water flowing in the use side refrigerant circuit onthe indoor units 71 side will be described. The direction of thebroken-line arrows in FIG. 13 indicates the direction of the water flowduring the heating only operation.

Water that has been heated in the first water-to-refrigerant heatexchanger 55B and second water-to-refrigerant heat exchanger 55C ispressurized in the respective pumps 60B and 60C, passes through thecorresponding first water pipings 61B and 61C, and is merged in each ofthe first water switching valves 72 a, 72 b, and 72 c. The water thathas been merged in the first water switching valves 72 a, 72 b, and 72 cpasses through the third water pipings 65 a, 65 b, and 65 c and flowsinto the indoor units 71 a, 71 b, and 71 c, respectively. The water thathas flowed into the indoor units 71 a, 71 b, and 71 c reduces itstemperature while heating the indoor air in the respective indoor sideheat exchangers 70 a, 70 b, and 70 c. The water that has reduced itstemperature in the indoor side heat exchangers 70 a, 70 b, and 70 cpasses through the fourth water pipings 66 a, 66 b, and 66 c and flowsinto the second water switching valves 73 a, 73 b, and 73 c,respectively. The water that has flowed into the second water switchingvalves 73 a, 73 b, and 73 c is each branched to the second water piping62B and the second water piping 62C and returns to the firstwater-to-refrigerant heat exchanger 55B and the secondwater-to-refrigerant heat exchanger 55C, respectively.

(Flow of Refrigerant During Heating Main Operation)

FIG. 14 is a diagram illustrating flows of the refrigerant in therefrigerant circuit of the air-conditioning apparatus during the heatingmain operation as an example of the refrigeration cycle apparatus ofEmbodiment 3 of the invention. Note that in FIG. 14, a case in which theindoor units 71 a and 71 b carry out heating operation and the indoorunit 71 c carries out cooling operation is illustrated. Further, duringthe heating main operation, the heat source side heat exchanger 3functions as an evaporator, the first water-to-refrigerant heatexchanger 55B functions as a condenser, and the secondwater-to-refrigerant heat exchanger 55C functions as an evaporator.

First, the flow of the refrigerant flowing in the heat source siderefrigerant circuit on the heat source unit A side will be described.The direction of the broken-line arrows in FIG. 14 indicates thedirection of the refrigerant flow during the heating main operation.

A high-temperature high-pressure gas refrigerant that has beendischarged from the compressor 1 flows into the four-way valve 2. Therefrigerant that has flowed out of the four-way valve 2, passes throughthe third check valve 4 c, the second heat source unit side connectingpiping 16A, and flows into the first branching unit 5 of the relay unitE′. The high-temperature high-pressure gas refrigerant that has flowedinto the first branching unit 5 passes through the solenoid valve 14Band the first water-to-refrigerant heat exchanger connecting piping 63Bin this order and flows into the first water-to-refrigerant heatexchanger 55B. Further, the high-temperature high-pressure gasrefrigerant that has flowed into the first water-to-refrigerant heatexchanger 55B exchanges heat with water and is condensed and liquefiedto heat the water. This refrigerant that has turned into a liquid statepasses through the flow control valve 11B whose opening degree, whichhas been controlled on the basis of the amount of subcooling at theoutlet of the first water-to-refrigerant heat exchanger 55B, is in anearly fully opened state, is slightly decompressed, and flows into thesecond branching unit 6 through the second water-to-refrigerant heatexchanger connecting piping 64B.

A portion of the refrigerant that has flowed into the second branchingunit 6 passes through the second water-to-refrigerant heat exchangerconnecting piping 64C and flows into the second water-to-refrigerantheat exchanger 55C that is about to cool water. This refrigerant entersthe flow control valve 11C that is controlled by the amount of superheatin the outlet of the second water-to-refrigerant heat exchanger 55C andis decompressed. The decompressed refrigerant exchanges heat in thesecond water-to-refrigerant heat exchanger 55C and is evaporated andgasified to cool the water. This refrigerant that has turned into agaseous state passes through the solenoid valve 13C and flows into thefirst heat source unit side connecting piping 15A.

Meanwhile, the remaining refrigerant in the second branching unit 6passes through the third flow control valve 9 that is controlled suchthat the pressure difference between the high pressure (for example, thepressure of the second heat source unit side connecting piping 16A) andthe middle pressure (for example, the pressures of the secondwater-to-refrigerant heat exchanger connecting pipings 64B and 64C) iswithin a predetermined range. Subsequently, this refrigerant merges inthe first heat source unit side connecting piping 15A with therefrigerant that has passed through the second water-to-refrigerant heatexchanger 55C.

The refrigerant that has been merged in the first heat source unit sideconnecting piping 15A flows into the heat source unit A, passes throughthe second check valve 4 b, and flows into the heat source side heatexchanger 3. Here, the refrigerant that has evaporated and has turnedinto a gaseous state after exchanging heat with the air sent from theair-sending device 18, which is capable of variably controlling thevolume of air, flows through the four-way valve 2 of the heat sourceunit and is sucked into the compressor 1.

During the heating main operation, since the solenoid valve 68 isclosed, the solenoid valve 14B is opened, and the solenoid valve 13B isclosed, the refrigerant flows in the direction of the broken-line arrowsin the first water-to-refrigerant heat exchanger connecting piping 63B,the first water-to-refrigerant heat exchanger 55B, and the secondwater-to-refrigerant heat exchanger connecting piping 64B, and heats thewater. Further, since the solenoid valve 14C is closed and the solenoidvalve 13C is opened, the refrigerant flows in the direction of thebroken-line arrows in the first water-to-refrigerant heat exchangerconnecting piping 63C, the second water-to-refrigerant heat exchanger55C, and the second water-to-refrigerant heat exchanger connectingpiping 64C, and cools the water. Further, since the first heat sourceunit side connecting piping 15A is low in pressure, the second heatsource unit side connecting piping 16A is high in pressure, the endconnection of the heat source side heat exchanger 3 to the switchingvalve 4 is low in pressure, and the end connection of the four-way valve2 to the switching valve 4 is high in pressure, the refrigerantinevitably flows to the second check valve 4 b and the third check valve4 c.

Next, the flow of water flowing in the use side refrigerant circuit onthe indoor units 71 side will be described. The direction of thebroken-line arrows in FIG. 14 indicate the direction of the flow ofwater that is used in the heating operation. The direction of the solidarrows in FIG. 14 indicates the direction of the flow of water that isused in the cooling operation.

Water that has been heated in the first water-to-refrigerant heatexchanger 55B is pressurized in the pump 60B, passes through the firstwater piping 61B, and flows into the first water switching valves 72 aand 72 b. The water that has flowed into the first water switchingvalves 72 a and 72 b passes through the third water pipings 65 a and 65b and flows into the indoor units 71 a and 71 b, respectively. The waterthat has flowed into the indoor units 71 a and 71 b reduces itstemperature while heating the indoor air in the respective indoor sideheat exchangers 70 a and 70 b. The water that has reduced itstemperature in the indoor side heat exchangers 70 a and 70 b passesthrough the fourth water pipings 66 a and 66 b and flows into the secondwater switching valves 73 a and 73 b, respectively. The water that hasflowed into the second water switching valves 73 a and 73 b returns tothe first water-to-refrigerant heat exchanger 55B.

Meanwhile, the water that has been heated in the secondwater-to-refrigerant heat exchanger 55C is pressurized in the pump 60C,passes through the first water piping 61C, and flows into the firstwater switching valve 72 c. The water that has flowed into the firstwater switching valve 72 c passes through the third water piping 65 cand flows into the indoor unit 71 c. The water that has flowed into theindoor unit 71 c increases its temperature while cooling the indoor airin the indoor side heat exchanger 70 c. The water that has been heatedin the indoor side heat exchanger 70 c passes through the fourth waterpiping 66 c and flows into the second water switching valve 73 c. Thewater that has flowed into the second water switching valve 73 c returnsto the second water-to-refrigerant heat exchanger 55C.

(Flow of Refrigerant During Cooling Main Operation)

FIG. 15 is a diagram illustrating flows of the refrigerant in therefrigerant circuit of the air-conditioning apparatus during the coolingmain operation as an example of the refrigeration cycle apparatus ofEmbodiment 3 of the invention. Note that in FIG. 15, a case in which theindoor unit 71 a carries out heating operation and the indoor units 71 band 71 c carry out cooling operation is illustrated. Further, during thecooling main operation, the heat source side heat exchanger 3 functionsas an condenser, the first water-to-refrigerant heat exchanger 55Bfunctions as a condenser, and the second water-to-refrigerant heatexchanger 55C functions as an evaporator.

First, the flow of the refrigerant flowing in the heat source siderefrigerant circuit on the heat source unit A side will be described.The direction of the solid arrows in FIG. 15 indicates the direction ofthe refrigerant flow during the cooling main operation.

A high-temperature high-pressure gas refrigerant that has beendischarged from the compressor 1 flows into the four-way valve 2. Therefrigerant that has flowed out of the four-way valve 2 flows into theheat source side heat exchanger 3. The refrigerant that has flowed intothe heat source side heat exchanger 3 exchanges heat with the air sentby the air-sending device 18 and is moderately condensed and liquefied,and turns into a high-temperature high-pressure two-phase refrigerant.The high-temperature high-pressure two-phase refrigerant, passes throughthe fourth check valve 4 d, the second heat source unit side connectingpiping 16A, and flows into the first branching unit 5 of the relay unitE′. The high-temperature high-pressure two-phase refrigerant that hasflowed into the first branching unit 5 passes through the solenoid valve13B and the first water-to-refrigerant heat exchanger connecting piping63B in this order and flows into the first water-to-refrigerant heatexchanger 55B. Further, the high-temperature high-pressure two-phaserefrigerant that has flowed into the first water-to-refrigerant heatexchanger 55B exchanges heat with water and is condensed and liquefiedto heat the water. This refrigerant that has turned into a liquid statepasses through the flow control valve 11B whose opening degree, whichhas been controlled on the basis of the amount of subcooling at theoutlet of the first water-to-refrigerant heat exchanger 55B, is in anearly fully opened state, is slightly decompressed, and flows into thesecond branching unit 6 through the second water-to-refrigerant heatexchanger connecting piping 64B.

The refrigerant that has flowed into the second branching unit 6 passesthrough the second water-to-refrigerant heat exchanger connecting piping64C and flows into the second water-to-refrigerant heat exchanger 55Cthat is about to cool water. This refrigerant enters the flow controlvalve 11C that is controlled by the amount of superheat in the outlet ofthe second water-to-refrigerant heat exchanger 55C and is decompressedto low pressure. The decompressed refrigerant exchanges heat in thesecond water-to-refrigerant heat exchanger 55C and is evaporated andgasified to cool the water. This refrigerant that has turned into agaseous state passes through the first water-to-refrigerant heatexchanger connecting piping 63C, the solenoid valve 13C, the firstbranching unit 5, the first heat source unit side connecting piping 15A,the first check valve 4 a, and the four-way valve 2, and is sucked intothe compressor 1.

During the cooling main operation, since the solenoid valve 68 isclosed, the solenoid valve 14B is opened, and the solenoid valve 13B isclosed, the refrigerant flows in the direction of the solid arrows inthe first water-to-refrigerant heat exchanger connecting piping 63B, thefirst water-to-refrigerant heat exchanger 55B, and the secondwater-to-refrigerant heat exchanger connecting piping 64B, and heats thewater. Further, since the solenoid valve 14C is closed and the solenoidvalve 13C is opened, the refrigerant flows in the direction of the solidarrows in the first water-to-refrigerant heat exchanger connectingpiping 63C, the second water-to-refrigerant heat exchanger 55C, and thesecond water-to-refrigerant heat exchanger connecting piping 64C, andcools the water. Further, since the first heat source unit sideconnecting piping 15A is low in pressure, the second heat source unitside connecting piping 16A is high in pressure, the end connection ofthe heat source side heat exchanger 3 to the switching valve 4 is highin pressure, and the end connection of the four-way valve 2 to theswitching valve 4 is low in pressure, the refrigerant inevitably flowsto the first check valve 4 a and the fourth check valve 4 d.

Next, the flow of water flowing in the use side refrigerant circuit onthe indoor units 71 side will be described. The direction of thebroken-line arrows in FIG. 15 indicate the direction of the flow ofwater that is used in the heating operation. The direction of the solidarrows in FIG. 15 indicates the direction of the flow of water that isused in the cooling operation.

Water that has been heated in the first water-to-refrigerant heatexchanger 55B is pressurized in the pump 60B, passes through the firstwater piping 61B, and flows into the first water switching valve 72 a.The water that has flowed into the first water switching valve 72 apasses through the third water piping 65 a and flows into the indoorunit 71 a. The water that has flowed into the indoor unit 71 a reducesits temperature while heating the indoor air in the indoor side heatexchanger 70 a. The water that has reduced its temperature in the indoorside heat exchanger 70 a passes through the fourth water piping 66 a andflows into the second water switching valve 73 a. The water that hasflowed into the second water switching valve 73 a returns to the firstwater-to-refrigerant heat exchanger 55B.

Meanwhile, the water that has been heated in the secondwater-to-refrigerant heat exchanger 55C is pressurized in the pump 60C,passes through the first water piping 61C, and flows into the firstwater switching valves 72 b and 72 c. The water that has flowed into thefirst water switching valves 72 b and 72 c passes through the thirdwater pipings 65 b and 65 c and flows into the indoor units 71 b and 71c, respectively. The water that has flowed into the indoor units 71 band 71 c increases its temperature while cooling the indoor air in therespective indoor side heat exchangers 70 b and 70 c. The water that hasbeen heated in the indoor side heat exchangers 70 b and 70 c passesthrough the fourth water pipings 66 b and 66 c and flows into the secondwater switching valves 73 b and 73 c, respectively. The water that hasflowed into the second water switching valve 73 c returns to the secondwater-to-refrigerant heat exchanger 55C.

Note that a control method of the heat exchange capacity of the heatsource side heat exchanger 3 is the same as that of Embodiment 1, andits description is omitted.

According to the above-configured air-conditioning apparatus, inaddition to the same advantageous effect of Embodiment 1, anadvantageous effect in which no refrigerant in the heat source siderefrigerant circuit will leak indoors can be obtained. Accordingly, aflammable and/or toxic natural refrigerant or a flammable and/or toxicrefrigerant that has high effect in suppressing global warming can beused in the heat source side refrigerant circuit. Thus, anair-conditioning apparatus that can secure both global warmingsuppressing effect and safety in the indoor space can be obtained.Furthermore, during the switching of the operation modes or during adefrost operation that may temporarily stop the compressor 1, theheating or cooling of the indoor space can be continued although onlyfor a short time since the latent heat of water can be used. Thus,advantageous effect such as increase in comfort can be obtained.

REFERENCE SIGNS LIST

A heat source unit; B, C, D indoor unit; E relay unit; 1 compressor; 2four-way valve; 3 heat source side heat exchanger; 3 a to 3 d solenoidvalve; 4 switching valve; 4 a first check valve; 4 c third check valve;4 d fourth check valve; 5 first branching unit; 6 second branching unit;7 gas-liquid separator; 8 flow control valve; 9 flow control valve; 10B,10C, 10D indoor unit side heat exchanger; 11B, 11C, 11D flow controlvalve; 13B, 13C, 13D solenoid valve; 14B, 14C, 14D solenoid valve; 15Afirst heat source unit side connecting piping; 15B, 15C, 15D firstindoor unit side connecting piping; 16A second heat source unit sideconnecting piping; 16B, 16C, 16D second indoor unit side connectingpiping; 18 air-sending device; 19 condensing temperature detectiondevice; 20 evaporating temperature detection device; 21 firstrefrigerant circuit; 22 second refrigerant circuit; 23 third refrigerantcircuit; 24 first heat exchanger; 25 second heat exchanger; 30distributor; 40 flow control valve; 50 bypass piping; 51 solenoid valve;55B first water-to-refrigerant heat exchanger; 55C secondwater-to-refrigerant heat exchanger; 60 pump; 61B, 61C first waterpiping; 62B, 62C second water piping; 63B, 63C firstwater-to-refrigerant heat exchanger connecting piping; 64B, 64C secondwater-to-refrigerant heat exchanger connecting piping; 65 third waterpiping; fourth water piping; 68 solenoid valve; 70 indoor side heatexchanger; indoor unit; 72 first water switching valve; 73 second waterswitching valve; 152 heat exchange capacity regulating device.

1. A refrigeration cycle apparatus, comprising: a heat source side heatexchanger including a plurality of heat exchangers connected inparallel; a supply device supplying, in a variable manner, an object tobe heat exchanged to the heat source side heat exchanger, the object tobe heat exchanged exchanging heat with a refrigerant that flows in theheat exchangers; passage on-off devices opening and closing refrigerantpassages of the heat exchangers, respectively; a bypass piping beingconnected to the heat exchangers in parallel; and a flow control devicebeing provided in the bypass piping, the flow control device controllinga flow rate of the refrigerant flowing in the bypass piping while someof passages to the plurality of heat exchangers are closed.
 2. Therefrigeration cycle apparatus of claim 1, further comprising adistributor regulating a gas-to-liquid ratio of a two-phase gas-liquidrefrigerant to a prescribed ratio and sending out the two-phasegas-liquid refrigerant to a downstream side, the distributor beingprovided to a junction of pipings connected to the respective heatexchangers and the bypass piping, the junction becoming the inlet sideof the heat exchangers when the heat exchangers operate as evaporators.3. The refrigeration cycle apparatus of claim 1, further comprising aconnecting piping serially connecting at least some of the heatexchangers among the plurality of heat exchangers; and an on-off valveopening and closing a passage of the connecting piping.
 4. Therefrigeration cycle apparatus of claim 3, wherein the heat exchangersserially connected by the connecting piping are disposed such that theobject to be heat exchanged that has exchanged heat in one of the heatexchangers that is on the downstream side in the refrigerant flowdirection is supplied to one of the heat exchangers that is on theupstream side in the refrigerant flow direction.
 5. The refrigerationcycle apparatus of claim 1, wherein the refrigerant flowing in the heatexchangers is a refrigerant that transfers heat to the object to be heatexchanged in a supercritical state without being condensed whentransferring heat to the object to be heat exchanged.